Imported Upstream version 2.15.0
[platform/upstream/git.git] / read-cache.c
index 6c8f395..65f4fe8 100644 (file)
@@ -5,6 +5,9 @@
  */
 #define NO_THE_INDEX_COMPATIBILITY_MACROS
 #include "cache.h"
+#include "config.h"
+#include "tempfile.h"
+#include "lockfile.h"
 #include "cache-tree.h"
 #include "refs.h"
 #include "dir.h"
 #include "commit.h"
 #include "blob.h"
 #include "resolve-undo.h"
+#include "strbuf.h"
+#include "varint.h"
+#include "split-index.h"
+#include "utf8.h"
 
-static struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really);
+/* Mask for the name length in ce_flags in the on-disk index */
+
+#define CE_NAMEMASK  (0x0fff)
 
 /* Index extensions.
  *
@@ -27,8 +36,16 @@ static struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int reall
 #define CACHE_EXT(s) ( (s[0]<<24)|(s[1]<<16)|(s[2]<<8)|(s[3]) )
 #define CACHE_EXT_TREE 0x54524545      /* "TREE" */
 #define CACHE_EXT_RESOLVE_UNDO 0x52455543 /* "REUC" */
+#define CACHE_EXT_LINK 0x6c696e6b        /* "link" */
+#define CACHE_EXT_UNTRACKED 0x554E5452   /* "UNTR" */
+
+/* changes that can be kept in $GIT_DIR/index (basically all extensions) */
+#define EXTMASK (RESOLVE_UNDO_CHANGED | CACHE_TREE_CHANGED | \
+                CE_ENTRY_ADDED | CE_ENTRY_REMOVED | CE_ENTRY_CHANGED | \
+                SPLIT_INDEX_ORDERED | UNTRACKED_CHANGED)
 
 struct index_state the_index;
+static const char *alternate_index_output;
 
 static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
 {
@@ -40,9 +57,12 @@ static void replace_index_entry(struct index_state *istate, int nr, struct cache
 {
        struct cache_entry *old = istate->cache[nr];
 
-       remove_name_hash(old);
+       replace_index_entry_in_base(istate, old, ce);
+       remove_name_hash(istate, old);
+       free(old);
        set_index_entry(istate, nr, ce);
-       istate->cache_changed = 1;
+       ce->ce_flags |= CE_UPDATE_IN_BASE;
+       istate->cache_changed |= CE_ENTRY_CHANGED;
 }
 
 void rename_index_entry_at(struct index_state *istate, int nr, const char *new_name)
@@ -52,15 +72,72 @@ void rename_index_entry_at(struct index_state *istate, int nr, const char *new_n
 
        new = xmalloc(cache_entry_size(namelen));
        copy_cache_entry(new, old);
-       new->ce_flags &= ~(CE_STATE_MASK | CE_NAMEMASK);
-       new->ce_flags |= (namelen >= CE_NAMEMASK ? CE_NAMEMASK : namelen);
+       new->ce_flags &= ~CE_HASHED;
+       new->ce_namelen = namelen;
+       new->index = 0;
        memcpy(new->name, new_name, namelen + 1);
 
-       cache_tree_invalidate_path(istate->cache_tree, old->name);
+       cache_tree_invalidate_path(istate, old->name);
+       untracked_cache_remove_from_index(istate, old->name);
        remove_index_entry_at(istate, nr);
        add_index_entry(istate, new, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
 }
 
+void fill_stat_data(struct stat_data *sd, struct stat *st)
+{
+       sd->sd_ctime.sec = (unsigned int)st->st_ctime;
+       sd->sd_mtime.sec = (unsigned int)st->st_mtime;
+       sd->sd_ctime.nsec = ST_CTIME_NSEC(*st);
+       sd->sd_mtime.nsec = ST_MTIME_NSEC(*st);
+       sd->sd_dev = st->st_dev;
+       sd->sd_ino = st->st_ino;
+       sd->sd_uid = st->st_uid;
+       sd->sd_gid = st->st_gid;
+       sd->sd_size = st->st_size;
+}
+
+int match_stat_data(const struct stat_data *sd, struct stat *st)
+{
+       int changed = 0;
+
+       if (sd->sd_mtime.sec != (unsigned int)st->st_mtime)
+               changed |= MTIME_CHANGED;
+       if (trust_ctime && check_stat &&
+           sd->sd_ctime.sec != (unsigned int)st->st_ctime)
+               changed |= CTIME_CHANGED;
+
+#ifdef USE_NSEC
+       if (check_stat && sd->sd_mtime.nsec != ST_MTIME_NSEC(*st))
+               changed |= MTIME_CHANGED;
+       if (trust_ctime && check_stat &&
+           sd->sd_ctime.nsec != ST_CTIME_NSEC(*st))
+               changed |= CTIME_CHANGED;
+#endif
+
+       if (check_stat) {
+               if (sd->sd_uid != (unsigned int) st->st_uid ||
+                       sd->sd_gid != (unsigned int) st->st_gid)
+                       changed |= OWNER_CHANGED;
+               if (sd->sd_ino != (unsigned int) st->st_ino)
+                       changed |= INODE_CHANGED;
+       }
+
+#ifdef USE_STDEV
+       /*
+        * st_dev breaks on network filesystems where different
+        * clients will have different views of what "device"
+        * the filesystem is on
+        */
+       if (check_stat && sd->sd_dev != (unsigned int) st->st_dev)
+                       changed |= INODE_CHANGED;
+#endif
+
+       if (sd->sd_size != (unsigned int) st->st_size)
+               changed |= DATA_CHANGED;
+
+       return changed;
+}
+
 /*
  * This only updates the "non-critical" parts of the directory
  * cache, ie the parts that aren't tracked by GIT, and only used
@@ -68,15 +145,7 @@ void rename_index_entry_at(struct index_state *istate, int nr, const char *new_n
  */
 void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
 {
-       ce->ce_ctime.sec = (unsigned int)st->st_ctime;
-       ce->ce_mtime.sec = (unsigned int)st->st_mtime;
-       ce->ce_ctime.nsec = ST_CTIME_NSEC(*st);
-       ce->ce_mtime.nsec = ST_MTIME_NSEC(*st);
-       ce->ce_dev = st->st_dev;
-       ce->ce_ino = st->st_ino;
-       ce->ce_uid = st->st_uid;
-       ce->ce_gid = st->st_gid;
-       ce->ce_size = st->st_size;
+       fill_stat_data(&ce->ce_stat_data, st);
 
        if (assume_unchanged)
                ce->ce_flags |= CE_VALID;
@@ -85,21 +154,21 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st)
                ce_mark_uptodate(ce);
 }
 
-static int ce_compare_data(struct cache_entry *ce, struct stat *st)
+static int ce_compare_data(const struct cache_entry *ce, struct stat *st)
 {
        int match = -1;
-       int fd = open(ce->name, O_RDONLY);
+       int fd = git_open_cloexec(ce->name, O_RDONLY);
 
        if (fd >= 0) {
-               unsigned char sha1[20];
-               if (!index_fd(sha1, fd, st, OBJ_BLOB, ce->name, 0))
-                       match = hashcmp(sha1, ce->sha1);
+               struct object_id oid;
+               if (!index_fd(&oid, fd, st, OBJ_BLOB, ce->name, 0))
+                       match = oidcmp(&oid, &ce->oid);
                /* index_fd() closed the file descriptor already */
        }
        return match;
 }
 
-static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
+static int ce_compare_link(const struct cache_entry *ce, size_t expected_size)
 {
        int match = -1;
        void *buffer;
@@ -110,7 +179,7 @@ static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
        if (strbuf_readlink(&sb, ce->name, expected_size))
                return -1;
 
-       buffer = read_sha1_file(ce->sha1, &type, &size);
+       buffer = read_sha1_file(ce->oid.hash, &type, &size);
        if (buffer) {
                if (size == sb.len)
                        match = memcmp(buffer, sb.buf, size);
@@ -120,7 +189,7 @@ static int ce_compare_link(struct cache_entry *ce, size_t expected_size)
        return match;
 }
 
-static int ce_compare_gitlink(struct cache_entry *ce)
+static int ce_compare_gitlink(const struct cache_entry *ce)
 {
        unsigned char sha1[20];
 
@@ -134,10 +203,10 @@ static int ce_compare_gitlink(struct cache_entry *ce)
         */
        if (resolve_gitlink_ref(ce->name, "HEAD", sha1) < 0)
                return 0;
-       return hashcmp(sha1, ce->sha1);
+       return hashcmp(sha1, ce->oid.hash);
 }
 
-static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
+static int ce_modified_check_fs(const struct cache_entry *ce, struct stat *st)
 {
        switch (st->st_mode & S_IFMT) {
        case S_IFREG:
@@ -151,13 +220,14 @@ static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st)
        case S_IFDIR:
                if (S_ISGITLINK(ce->ce_mode))
                        return ce_compare_gitlink(ce) ? DATA_CHANGED : 0;
+               /* else fallthrough */
        default:
                return TYPE_CHANGED;
        }
        return 0;
 }
 
-static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
+static int ce_match_stat_basic(const struct cache_entry *ce, struct stat *st)
 {
        unsigned int changed = 0;
 
@@ -189,63 +259,50 @@ static int ce_match_stat_basic(struct cache_entry *ce, struct stat *st)
        default:
                die("internal error: ce_mode is %o", ce->ce_mode);
        }
-       if (ce->ce_mtime.sec != (unsigned int)st->st_mtime)
-               changed |= MTIME_CHANGED;
-       if (trust_ctime && ce->ce_ctime.sec != (unsigned int)st->st_ctime)
-               changed |= CTIME_CHANGED;
-
-#ifdef USE_NSEC
-       if (ce->ce_mtime.nsec != ST_MTIME_NSEC(*st))
-               changed |= MTIME_CHANGED;
-       if (trust_ctime && ce->ce_ctime.nsec != ST_CTIME_NSEC(*st))
-               changed |= CTIME_CHANGED;
-#endif
 
-       if (ce->ce_uid != (unsigned int) st->st_uid ||
-           ce->ce_gid != (unsigned int) st->st_gid)
-               changed |= OWNER_CHANGED;
-       if (ce->ce_ino != (unsigned int) st->st_ino)
-               changed |= INODE_CHANGED;
-
-#ifdef USE_STDEV
-       /*
-        * st_dev breaks on network filesystems where different
-        * clients will have different views of what "device"
-        * the filesystem is on
-        */
-       if (ce->ce_dev != (unsigned int) st->st_dev)
-               changed |= INODE_CHANGED;
-#endif
-
-       if (ce->ce_size != (unsigned int) st->st_size)
-               changed |= DATA_CHANGED;
+       changed |= match_stat_data(&ce->ce_stat_data, st);
 
        /* Racily smudged entry? */
-       if (!ce->ce_size) {
-               if (!is_empty_blob_sha1(ce->sha1))
+       if (!ce->ce_stat_data.sd_size) {
+               if (!is_empty_blob_sha1(ce->oid.hash))
                        changed |= DATA_CHANGED;
        }
 
        return changed;
 }
 
-static int is_racy_timestamp(const struct index_state *istate, struct cache_entry *ce)
+static int is_racy_stat(const struct index_state *istate,
+                       const struct stat_data *sd)
 {
-       return (!S_ISGITLINK(ce->ce_mode) &&
-               istate->timestamp.sec &&
+       return (istate->timestamp.sec &&
 #ifdef USE_NSEC
                 /* nanosecond timestamped files can also be racy! */
-               (istate->timestamp.sec < ce->ce_mtime.sec ||
-                (istate->timestamp.sec == ce->ce_mtime.sec &&
-                 istate->timestamp.nsec <= ce->ce_mtime.nsec))
+               (istate->timestamp.sec < sd->sd_mtime.sec ||
+                (istate->timestamp.sec == sd->sd_mtime.sec &&
+                 istate->timestamp.nsec <= sd->sd_mtime.nsec))
 #else
-               istate->timestamp.sec <= ce->ce_mtime.sec
+               istate->timestamp.sec <= sd->sd_mtime.sec
 #endif
-                );
+               );
+}
+
+static int is_racy_timestamp(const struct index_state *istate,
+                            const struct cache_entry *ce)
+{
+       return (!S_ISGITLINK(ce->ce_mode) &&
+               is_racy_stat(istate, &ce->ce_stat_data));
+}
+
+int match_stat_data_racy(const struct index_state *istate,
+                        const struct stat_data *sd, struct stat *st)
+{
+       if (is_racy_stat(istate, sd))
+               return MTIME_CHANGED;
+       return match_stat_data(sd, st);
 }
 
 int ie_match_stat(const struct index_state *istate,
-                 struct cache_entry *ce, struct stat *st,
+                 const struct cache_entry *ce, struct stat *st,
                  unsigned int options)
 {
        unsigned int changed;
@@ -269,7 +326,7 @@ int ie_match_stat(const struct index_state *istate,
         * by definition never matches what is in the work tree until it
         * actually gets added.
         */
-       if (ce->ce_flags & CE_INTENT_TO_ADD)
+       if (ce_intent_to_add(ce))
                return DATA_CHANGED | TYPE_CHANGED | MODE_CHANGED;
 
        changed = ce_match_stat_basic(ce, st);
@@ -301,7 +358,8 @@ int ie_match_stat(const struct index_state *istate,
 }
 
 int ie_modified(const struct index_state *istate,
-               struct cache_entry *ce, struct stat *st, unsigned int options)
+               const struct cache_entry *ce,
+               struct stat *st, unsigned int options)
 {
        int changed, changed_fs;
 
@@ -330,7 +388,7 @@ int ie_modified(const struct index_state *istate,
         * then we know it is.
         */
        if ((changed & DATA_CHANGED) &&
-           (S_ISGITLINK(ce->ce_mode) || ce->ce_size != 0))
+           (S_ISGITLINK(ce->ce_mode) || ce->ce_stat_data.sd_size != 0))
                return changed;
 
        changed_fs = ce_modified_check_fs(ce, st);
@@ -393,33 +451,35 @@ int df_name_compare(const char *name1, int len1, int mode1,
        return c1 - c2;
 }
 
-int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
+int name_compare(const char *name1, size_t len1, const char *name2, size_t len2)
 {
-       int len1 = flags1 & CE_NAMEMASK;
-       int len2 = flags2 & CE_NAMEMASK;
-       int len = len1 < len2 ? len1 : len2;
-       int cmp;
-
-       cmp = memcmp(name1, name2, len);
+       size_t min_len = (len1 < len2) ? len1 : len2;
+       int cmp = memcmp(name1, name2, min_len);
        if (cmp)
                return cmp;
        if (len1 < len2)
                return -1;
        if (len1 > len2)
                return 1;
+       return 0;
+}
 
-       /* Compare stages  */
-       flags1 &= CE_STAGEMASK;
-       flags2 &= CE_STAGEMASK;
+int cache_name_stage_compare(const char *name1, int len1, int stage1, const char *name2, int len2, int stage2)
+{
+       int cmp;
 
-       if (flags1 < flags2)
+       cmp = name_compare(name1, len1, name2, len2);
+       if (cmp)
+               return cmp;
+
+       if (stage1 < stage2)
                return -1;
-       if (flags1 > flags2)
+       if (stage1 > stage2)
                return 1;
        return 0;
 }
 
-int index_name_pos(const struct index_state *istate, const char *name, int namelen)
+static int index_name_stage_pos(const struct index_state *istate, const char *name, int namelen, int stage)
 {
        int first, last;
 
@@ -428,7 +488,7 @@ int index_name_pos(const struct index_state *istate, const char *name, int namel
        while (last > first) {
                int next = (last + first) >> 1;
                struct cache_entry *ce = istate->cache[next];
-               int cmp = cache_name_compare(name, namelen, ce->name, ce->ce_flags);
+               int cmp = cache_name_stage_compare(name, namelen, stage, ce->name, ce_namelen(ce), ce_stage(ce));
                if (!cmp)
                        return next;
                if (cmp < 0) {
@@ -440,25 +500,29 @@ int index_name_pos(const struct index_state *istate, const char *name, int namel
        return -first-1;
 }
 
-/* Remove entry, return true if there are more entries to go.. */
+int index_name_pos(const struct index_state *istate, const char *name, int namelen)
+{
+       return index_name_stage_pos(istate, name, namelen, 0);
+}
+
 int remove_index_entry_at(struct index_state *istate, int pos)
 {
        struct cache_entry *ce = istate->cache[pos];
 
        record_resolve_undo(istate, ce);
-       remove_name_hash(ce);
-       istate->cache_changed = 1;
+       remove_name_hash(istate, ce);
+       save_or_free_index_entry(istate, ce);
+       istate->cache_changed |= CE_ENTRY_REMOVED;
        istate->cache_nr--;
        if (pos >= istate->cache_nr)
                return 0;
-       memmove(istate->cache + pos,
-               istate->cache + pos + 1,
-               (istate->cache_nr - pos) * sizeof(struct cache_entry *));
+       MOVE_ARRAY(istate->cache + pos, istate->cache + pos + 1,
+                  istate->cache_nr - pos);
        return 1;
 }
 
 /*
- * Remove all cache ententries marked for removal, that is where
+ * Remove all cache entries marked for removal, that is where
  * CE_REMOVE is set in ce_flags.  This is much more effective than
  * calling remove_index_entry_at() for each entry to be removed.
  */
@@ -468,12 +532,16 @@ void remove_marked_cache_entries(struct index_state *istate)
        unsigned int i, j;
 
        for (i = j = 0; i < istate->cache_nr; i++) {
-               if (ce_array[i]->ce_flags & CE_REMOVE)
-                       remove_name_hash(ce_array[i]);
+               if (ce_array[i]->ce_flags & CE_REMOVE) {
+                       remove_name_hash(istate, ce_array[i]);
+                       save_or_free_index_entry(istate, ce_array[i]);
+               }
                else
                        ce_array[j++] = ce_array[i];
        }
-       istate->cache_changed = 1;
+       if (j == istate->cache_nr)
+               return;
+       istate->cache_changed |= CE_ENTRY_REMOVED;
        istate->cache_nr = j;
 }
 
@@ -482,7 +550,8 @@ int remove_file_from_index(struct index_state *istate, const char *path)
        int pos = index_name_pos(istate, path, strlen(path));
        if (pos < 0)
                pos = -pos-1;
-       cache_tree_invalidate_path(istate->cache_tree, path);
+       cache_tree_invalidate_path(istate, path);
+       untracked_cache_remove_from_index(istate, path);
        while (pos < istate->cache_nr && !strcmp(istate->cache[pos]->name, path))
                remove_index_entry_at(istate, pos);
        return 0;
@@ -531,7 +600,9 @@ static int different_name(struct cache_entry *ce, struct cache_entry *alias)
  * So we use the CE_ADDED flag to verify that the alias was an old
  * one before we accept it as
  */
-static struct cache_entry *create_alias_ce(struct cache_entry *ce, struct cache_entry *alias)
+static struct cache_entry *create_alias_ce(struct index_state *istate,
+                                          struct cache_entry *ce,
+                                          struct cache_entry *alias)
 {
        int len;
        struct cache_entry *new;
@@ -544,16 +615,16 @@ static struct cache_entry *create_alias_ce(struct cache_entry *ce, struct cache_
        new = xcalloc(1, cache_entry_size(len));
        memcpy(new->name, alias->name, len);
        copy_cache_entry(new, ce);
-       free(ce);
+       save_or_free_index_entry(istate, ce);
        return new;
 }
 
-static void record_intent_to_add(struct cache_entry *ce)
+void set_object_name_for_intent_to_add_entry(struct cache_entry *ce)
 {
        unsigned char sha1[20];
        if (write_sha1_file("", 0, blob_type, sha1))
                die("cannot create an empty blob in the object database");
-       hashcpy(ce->sha1, sha1);
+       hashcpy(ce->oid.hash, sha1);
 }
 
 int add_to_index(struct index_state *istate, const char *path, struct stat *st, int flags)
@@ -579,15 +650,16 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
        size = cache_entry_size(namelen);
        ce = xcalloc(1, size);
        memcpy(ce->name, path, namelen);
-       ce->ce_flags = namelen;
+       ce->ce_namelen = namelen;
        if (!intent_only)
                fill_stat_cache_info(ce, st);
        else
                ce->ce_flags |= CE_INTENT_TO_ADD;
 
-       if (trust_executable_bit && has_symlinks)
+
+       if (trust_executable_bit && has_symlinks) {
                ce->ce_mode = create_ce_mode(st_mode);
-       else {
+       else {
                /* If there is an existing entry, pick the mode bits and type
                 * from it, otherwise assume unexecutable regular file.
                 */
@@ -604,52 +676,43 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
         * entry's directory case.
         */
        if (ignore_case) {
-               const char *startPtr = ce->name;
-               const char *ptr = startPtr;
-               while (*ptr) {
-                       while (*ptr && *ptr != '/')
-                               ++ptr;
-                       if (*ptr == '/') {
-                               struct cache_entry *foundce;
-                               ++ptr;
-                               foundce = index_name_exists(&the_index, ce->name, ptr - ce->name, ignore_case);
-                               if (foundce) {
-                                       memcpy((void *)startPtr, foundce->name + (startPtr - ce->name), ptr - startPtr);
-                                       startPtr = ptr;
-                               }
-                       }
-               }
+               adjust_dirname_case(istate, ce->name);
        }
 
-       alias = index_name_exists(istate, ce->name, ce_namelen(ce), ignore_case);
+       alias = index_file_exists(istate, ce->name, ce_namelen(ce), ignore_case);
        if (alias && !ce_stage(alias) && !ie_match_stat(istate, alias, st, ce_option)) {
                /* Nothing changed, really */
-               free(ce);
                if (!S_ISGITLINK(alias->ce_mode))
                        ce_mark_uptodate(alias);
                alias->ce_flags |= CE_ADDED;
+
+               free(ce);
                return 0;
        }
        if (!intent_only) {
-               if (index_path(ce->sha1, path, st, HASH_WRITE_OBJECT))
+               if (index_path(&ce->oid, path, st, HASH_WRITE_OBJECT)) {
+                       free(ce);
                        return error("unable to index file %s", path);
+               }
        } else
-               record_intent_to_add(ce);
+               set_object_name_for_intent_to_add_entry(ce);
 
        if (ignore_case && alias && different_name(ce, alias))
-               ce = create_alias_ce(ce, alias);
+               ce = create_alias_ce(istate, ce, alias);
        ce->ce_flags |= CE_ADDED;
 
        /* It was suspected to be racily clean, but it turns out to be Ok */
        was_same = (alias &&
                    !ce_stage(alias) &&
-                   !hashcmp(alias->sha1, ce->sha1) &&
+                   !oidcmp(&alias->oid, &ce->oid) &&
                    ce->ce_mode == alias->ce_mode);
 
        if (pretend)
-               ;
-       else if (add_index_entry(istate, ce, add_option))
-               return error("unable to add %s to index",path);
+               free(ce);
+       else if (add_index_entry(istate, ce, add_option)) {
+               free(ce);
+               return error("unable to add %s to index", path);
+       }
        if (verbose && !was_same)
                printf("add '%s'\n", path);
        return 0;
@@ -665,10 +728,10 @@ int add_file_to_index(struct index_state *istate, const char *path, int flags)
 
 struct cache_entry *make_cache_entry(unsigned int mode,
                const unsigned char *sha1, const char *path, int stage,
-               int refresh)
+               unsigned int refresh_options)
 {
        int size, len;
-       struct cache_entry *ce;
+       struct cache_entry *ce, *ret;
 
        if (!verify_path(path)) {
                error("Invalid path '%s'", path);
@@ -679,26 +742,51 @@ struct cache_entry *make_cache_entry(unsigned int mode,
        size = cache_entry_size(len);
        ce = xcalloc(1, size);
 
-       hashcpy(ce->sha1, sha1);
+       hashcpy(ce->oid.hash, sha1);
        memcpy(ce->name, path, len);
-       ce->ce_flags = create_ce_flags(len, stage);
+       ce->ce_flags = create_ce_flags(stage);
+       ce->ce_namelen = len;
        ce->ce_mode = create_ce_mode(mode);
 
-       if (refresh)
-               return refresh_cache_entry(ce, 0);
-
-       return ce;
+       ret = refresh_cache_entry(ce, refresh_options);
+       if (ret != ce)
+               free(ce);
+       return ret;
 }
 
-int ce_same_name(struct cache_entry *a, struct cache_entry *b)
+/*
+ * Chmod an index entry with either +x or -x.
+ *
+ * Returns -1 if the chmod for the particular cache entry failed (if it's
+ * not a regular file), -2 if an invalid flip argument is passed in, 0
+ * otherwise.
+ */
+int chmod_index_entry(struct index_state *istate, struct cache_entry *ce,
+                     char flip)
 {
-       int len = ce_namelen(a);
-       return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
+       if (!S_ISREG(ce->ce_mode))
+               return -1;
+       switch (flip) {
+       case '+':
+               ce->ce_mode |= 0111;
+               break;
+       case '-':
+               ce->ce_mode &= ~0111;
+               break;
+       default:
+               return -2;
+       }
+       cache_tree_invalidate_path(istate, ce->name);
+       ce->ce_flags |= CE_UPDATE_IN_BASE;
+       istate->cache_changed |= CE_ENTRY_CHANGED;
+
+       return 0;
 }
 
-int ce_path_match(const struct cache_entry *ce, const struct pathspec *pathspec)
+int ce_same_name(const struct cache_entry *a, const struct cache_entry *b)
 {
-       return match_pathspec_depth(pathspec, ce->name, ce_namelen(ce), 0, NULL);
+       int len = ce_namelen(a);
+       return ce_namelen(b) == len && !memcmp(a->name, b->name, len);
 }
 
 /*
@@ -727,9 +815,10 @@ static int verify_dotfile(const char *rest)
         * shares the path end test with the ".." case.
         */
        case 'g':
-               if (rest[1] != 'i')
+       case 'G':
+               if (rest[1] != 'i' && rest[1] != 'I')
                        break;
-               if (rest[2] != 't')
+               if (rest[2] != 't' && rest[2] != 'T')
                        break;
                rest += 2;
        /* fallthrough */
@@ -753,6 +842,10 @@ int verify_path(const char *path)
                        return 1;
                if (is_dir_sep(c)) {
 inside:
+                       if (protect_hfs && is_hfs_dotgit(path))
+                               return 0;
+                       if (protect_ntfs && is_ntfs_dotgit(path))
+                               return 0;
                        c = *path++;
                        if ((c == '.' && !verify_dotfile(path)) ||
                            is_dir_sep(c) || c == '\0')
@@ -795,9 +888,32 @@ static int has_file_name(struct index_state *istate,
        return retval;
 }
 
+
+/*
+ * Like strcmp(), but also return the offset of the first change.
+ * If strings are equal, return the length.
+ */
+int strcmp_offset(const char *s1, const char *s2, size_t *first_change)
+{
+       size_t k;
+
+       if (!first_change)
+               return strcmp(s1, s2);
+
+       for (k = 0; s1[k] == s2[k]; k++)
+               if (s1[k] == '\0')
+                       break;
+
+       *first_change = k;
+       return (unsigned char)s1[k] - (unsigned char)s2[k];
+}
+
 /*
  * Do we have another file with a pathname that is a proper
  * subset of the name we're trying to add?
+ *
+ * That is, is there another file in the index with a path
+ * that matches a sub-directory in the given entry?
  */
 static int has_dir_name(struct index_state *istate,
                        const struct cache_entry *ce, int pos, int ok_to_replace)
@@ -806,9 +922,51 @@ static int has_dir_name(struct index_state *istate,
        int stage = ce_stage(ce);
        const char *name = ce->name;
        const char *slash = name + ce_namelen(ce);
+       size_t len_eq_last;
+       int cmp_last = 0;
+
+       /*
+        * We are frequently called during an iteration on a sorted
+        * list of pathnames and while building a new index.  Therefore,
+        * there is a high probability that this entry will eventually
+        * be appended to the index, rather than inserted in the middle.
+        * If we can confirm that, we can avoid binary searches on the
+        * components of the pathname.
+        *
+        * Compare the entry's full path with the last path in the index.
+        */
+       if (istate->cache_nr > 0) {
+               cmp_last = strcmp_offset(name,
+                       istate->cache[istate->cache_nr - 1]->name,
+                       &len_eq_last);
+               if (cmp_last > 0) {
+                       if (len_eq_last == 0) {
+                               /*
+                                * The entry sorts AFTER the last one in the
+                                * index and their paths have no common prefix,
+                                * so there cannot be a F/D conflict.
+                                */
+                               return retval;
+                       } else {
+                               /*
+                                * The entry sorts AFTER the last one in the
+                                * index, but has a common prefix.  Fall through
+                                * to the loop below to disect the entry's path
+                                * and see where the difference is.
+                                */
+                       }
+               } else if (cmp_last == 0) {
+                       /*
+                        * The entry exactly matches the last one in the
+                        * index, but because of multiple stage and CE_REMOVE
+                        * items, we fall through and let the regular search
+                        * code handle it.
+                        */
+               }
+       }
 
        for (;;) {
-               int len;
+               size_t len;
 
                for (;;) {
                        if (*--slash == '/')
@@ -818,7 +976,68 @@ static int has_dir_name(struct index_state *istate,
                }
                len = slash - name;
 
-               pos = index_name_pos(istate, name, create_ce_flags(len, stage));
+               if (cmp_last > 0) {
+                       /*
+                        * (len + 1) is a directory boundary (including
+                        * the trailing slash).  And since the loop is
+                        * decrementing "slash", the first iteration is
+                        * the longest directory prefix; subsequent
+                        * iterations consider parent directories.
+                        */
+
+                       if (len + 1 <= len_eq_last) {
+                               /*
+                                * The directory prefix (including the trailing
+                                * slash) also appears as a prefix in the last
+                                * entry, so the remainder cannot collide (because
+                                * strcmp said the whole path was greater).
+                                *
+                                * EQ: last: xxx/A
+                                *     this: xxx/B
+                                *
+                                * LT: last: xxx/file_A
+                                *     this: xxx/file_B
+                                */
+                               return retval;
+                       }
+
+                       if (len > len_eq_last) {
+                               /*
+                                * This part of the directory prefix (excluding
+                                * the trailing slash) is longer than the known
+                                * equal portions, so this sub-directory cannot
+                                * collide with a file.
+                                *
+                                * GT: last: xxxA
+                                *     this: xxxB/file
+                                */
+                               return retval;
+                       }
+
+                       if (istate->cache_nr > 0 &&
+                               ce_namelen(istate->cache[istate->cache_nr - 1]) > len) {
+                               /*
+                                * The directory prefix lines up with part of
+                                * a longer file or directory name, but sorts
+                                * after it, so this sub-directory cannot
+                                * collide with a file.
+                                *
+                                * last: xxx/yy-file (because '-' sorts before '/')
+                                * this: xxx/yy/abc
+                                */
+                               return retval;
+                       }
+
+                       /*
+                        * This is a possible collision. Fall through and
+                        * let the regular search code handle it.
+                        *
+                        * last: xxx
+                        * this: xxx/file
+                        */
+               }
+
+               pos = index_name_stage_pos(istate, name, len, stage);
                if (pos >= 0) {
                        /*
                         * Found one, but not so fast.  This could
@@ -907,8 +1126,18 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
        int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
        int new_only = option & ADD_CACHE_NEW_ONLY;
 
-       cache_tree_invalidate_path(istate->cache_tree, ce->name);
-       pos = index_name_pos(istate, ce->name, ce->ce_flags);
+       if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
+               cache_tree_invalidate_path(istate, ce->name);
+
+       /*
+        * If this entry's path sorts after the last entry in the index,
+        * we can avoid searching for it.
+        */
+       if (istate->cache_nr > 0 &&
+               strcmp(ce->name, istate->cache[istate->cache_nr - 1]->name) > 0)
+               pos = -istate->cache_nr - 1;
+       else
+               pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
 
        /* existing match? Just replace it. */
        if (pos >= 0) {
@@ -918,6 +1147,9 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
        }
        pos = -pos-1;
 
+       if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
+               untracked_cache_add_to_index(istate, ce->name);
+
        /*
         * Inserting a merged entry ("stage 0") into the index
         * will always replace all non-merged entries..
@@ -940,7 +1172,7 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
                if (!ok_to_replace)
                        return error("'%s' appears as both a file and as a directory",
                                     ce->name);
-               pos = index_name_pos(istate, ce->name, ce->ce_flags);
+               pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
                pos = -pos-1;
        }
        return pos + 1;
@@ -961,11 +1193,7 @@ int add_index_entry(struct index_state *istate, struct cache_entry *ce, int opti
        }
 
        /* Make sure the array is big enough .. */
-       if (istate->cache_nr == istate->cache_alloc) {
-               istate->cache_alloc = alloc_nr(istate->cache_alloc);
-               istate->cache = xrealloc(istate->cache,
-                                       istate->cache_alloc * sizeof(struct cache_entry *));
-       }
+       ALLOC_GROW(istate->cache, istate->cache_nr + 1, istate->cache_alloc);
 
        /* Add it in.. */
        istate->cache_nr++;
@@ -974,7 +1202,7 @@ int add_index_entry(struct index_state *istate, struct cache_entry *ce, int opti
                        istate->cache + pos,
                        (istate->cache_nr - pos - 1) * sizeof(ce));
        set_index_entry(istate, pos, ce);
-       istate->cache_changed = 1;
+       istate->cache_changed |= CE_ENTRY_ADDED;
        return 0;
 }
 
@@ -997,10 +1225,12 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
        struct stat st;
        struct cache_entry *updated;
        int changed, size;
+       int refresh = options & CE_MATCH_REFRESH;
        int ignore_valid = options & CE_MATCH_IGNORE_VALID;
        int ignore_skip_worktree = options & CE_MATCH_IGNORE_SKIP_WORKTREE;
+       int ignore_missing = options & CE_MATCH_IGNORE_MISSING;
 
-       if (ce_uptodate(ce))
+       if (!refresh || ce_uptodate(ce))
                return ce;
 
        /*
@@ -1017,7 +1247,17 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
                return ce;
        }
 
+       if (has_symlink_leading_path(ce->name, ce_namelen(ce))) {
+               if (ignore_missing)
+                       return ce;
+               if (err)
+                       *err = ENOENT;
+               return NULL;
+       }
+
        if (lstat(ce->name, &st) < 0) {
+               if (ignore_missing && errno == ENOENT)
+                       return ce;
                if (err)
                        *err = errno;
                return NULL;
@@ -1069,6 +1309,7 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
            !(ce->ce_flags & CE_VALID))
                updated->ce_flags &= ~CE_VALID;
 
+       /* istate->cache_changed is updated in the caller */
        return updated;
 }
 
@@ -1082,7 +1323,8 @@ static void show_file(const char * fmt, const char * name, int in_porcelain,
        printf(fmt, name);
 }
 
-int refresh_index(struct index_state *istate, unsigned int flags, const char **pathspec,
+int refresh_index(struct index_state *istate, unsigned int flags,
+                 const struct pathspec *pathspec,
                  char *seen, const char *header_msg)
 {
        int i;
@@ -1094,7 +1336,9 @@ int refresh_index(struct index_state *istate, unsigned int flags, const char **p
        int ignore_submodules = (flags & REFRESH_IGNORE_SUBMODULES) != 0;
        int first = 1;
        int in_porcelain = (flags & REFRESH_IN_PORCELAIN);
-       unsigned int options = really ? CE_MATCH_IGNORE_VALID : 0;
+       unsigned int options = (CE_MATCH_REFRESH |
+                               (really ? CE_MATCH_IGNORE_VALID : 0) |
+                               (not_new ? CE_MATCH_IGNORE_MISSING : 0));
        const char *modified_fmt;
        const char *deleted_fmt;
        const char *typechange_fmt;
@@ -1116,8 +1360,7 @@ int refresh_index(struct index_state *istate, unsigned int flags, const char **p
                if (ignore_submodules && S_ISGITLINK(ce->ce_mode))
                        continue;
 
-               if (pathspec &&
-                   !match_pathspec(pathspec, ce->name, strlen(ce->name), 0, seen))
+               if (pathspec && !ce_path_match(ce, pathspec, seen))
                        filtered = 1;
 
                if (ce_stage(ce)) {
@@ -1143,21 +1386,20 @@ int refresh_index(struct index_state *istate, unsigned int flags, const char **p
                if (!new) {
                        const char *fmt;
 
-                       if (not_new && cache_errno == ENOENT)
-                               continue;
                        if (really && cache_errno == EINVAL) {
                                /* If we are doing --really-refresh that
                                 * means the index is not valid anymore.
                                 */
                                ce->ce_flags &= ~CE_VALID;
-                               istate->cache_changed = 1;
+                               ce->ce_flags |= CE_UPDATE_IN_BASE;
+                               istate->cache_changed |= CE_ENTRY_CHANGED;
                        }
                        if (quiet)
                                continue;
 
                        if (cache_errno == ENOENT)
                                fmt = deleted_fmt;
-                       else if (ce->ce_flags & CE_INTENT_TO_ADD)
+                       else if (ce_intent_to_add(ce))
                                fmt = added_fmt; /* must be before other checks */
                        else if (changed & TYPE_CHANGED)
                                fmt = typechange_fmt;
@@ -1174,20 +1416,116 @@ int refresh_index(struct index_state *istate, unsigned int flags, const char **p
        return has_errors;
 }
 
-static struct cache_entry *refresh_cache_entry(struct cache_entry *ce, int really)
+struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
+                                              unsigned int options)
+{
+       return refresh_cache_ent(&the_index, ce, options, NULL, NULL);
+}
+
+
+/*****************************************************************
+ * Index File I/O
+ *****************************************************************/
+
+#define INDEX_FORMAT_DEFAULT 3
+
+static unsigned int get_index_format_default(void)
 {
-       return refresh_cache_ent(&the_index, ce, really, NULL, NULL);
+       char *envversion = getenv("GIT_INDEX_VERSION");
+       char *endp;
+       int value;
+       unsigned int version = INDEX_FORMAT_DEFAULT;
+
+       if (!envversion) {
+               if (!git_config_get_int("index.version", &value))
+                       version = value;
+               if (version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < version) {
+                       warning(_("index.version set, but the value is invalid.\n"
+                                 "Using version %i"), INDEX_FORMAT_DEFAULT);
+                       return INDEX_FORMAT_DEFAULT;
+               }
+               return version;
+       }
+
+       version = strtoul(envversion, &endp, 10);
+       if (*endp ||
+           version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < version) {
+               warning(_("GIT_INDEX_VERSION set, but the value is invalid.\n"
+                         "Using version %i"), INDEX_FORMAT_DEFAULT);
+               version = INDEX_FORMAT_DEFAULT;
+       }
+       return version;
 }
 
+/*
+ * dev/ino/uid/gid/size are also just tracked to the low 32 bits
+ * Again - this is just a (very strong in practice) heuristic that
+ * the inode hasn't changed.
+ *
+ * We save the fields in big-endian order to allow using the
+ * index file over NFS transparently.
+ */
+struct ondisk_cache_entry {
+       struct cache_time ctime;
+       struct cache_time mtime;
+       uint32_t dev;
+       uint32_t ino;
+       uint32_t mode;
+       uint32_t uid;
+       uint32_t gid;
+       uint32_t size;
+       unsigned char sha1[20];
+       uint16_t flags;
+       char name[FLEX_ARRAY]; /* more */
+};
+
+/*
+ * This struct is used when CE_EXTENDED bit is 1
+ * The struct must match ondisk_cache_entry exactly from
+ * ctime till flags
+ */
+struct ondisk_cache_entry_extended {
+       struct cache_time ctime;
+       struct cache_time mtime;
+       uint32_t dev;
+       uint32_t ino;
+       uint32_t mode;
+       uint32_t uid;
+       uint32_t gid;
+       uint32_t size;
+       unsigned char sha1[20];
+       uint16_t flags;
+       uint16_t flags2;
+       char name[FLEX_ARRAY]; /* more */
+};
+
+/* These are only used for v3 or lower */
+#define align_padding_size(size, len) ((size + (len) + 8) & ~7) - (size + len)
+#define align_flex_name(STRUCT,len) ((offsetof(struct STRUCT,name) + (len) + 8) & ~7)
+#define ondisk_cache_entry_size(len) align_flex_name(ondisk_cache_entry,len)
+#define ondisk_cache_entry_extended_size(len) align_flex_name(ondisk_cache_entry_extended,len)
+#define ondisk_ce_size(ce) (((ce)->ce_flags & CE_EXTENDED) ? \
+                           ondisk_cache_entry_extended_size(ce_namelen(ce)) : \
+                           ondisk_cache_entry_size(ce_namelen(ce)))
+
+/* Allow fsck to force verification of the index checksum. */
+int verify_index_checksum;
+
 static int verify_hdr(struct cache_header *hdr, unsigned long size)
 {
        git_SHA_CTX c;
        unsigned char sha1[20];
+       int hdr_version;
 
        if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
                return error("bad signature");
-       if (hdr->hdr_version != htonl(2) && hdr->hdr_version != htonl(3))
-               return error("bad index version");
+       hdr_version = ntohl(hdr->hdr_version);
+       if (hdr_version < INDEX_FORMAT_LB || INDEX_FORMAT_UB < hdr_version)
+               return error("bad index version %d", hdr_version);
+
+       if (!verify_index_checksum)
+               return 0;
+
        git_SHA1_Init(&c);
        git_SHA1_Update(&c, hdr, size - 20);
        git_SHA1_Final(sha1, &c);
@@ -1206,6 +1544,13 @@ static int read_index_extension(struct index_state *istate,
        case CACHE_EXT_RESOLVE_UNDO:
                istate->resolve_undo = resolve_undo_read(data, sz);
                break;
+       case CACHE_EXT_LINK:
+               if (read_link_extension(istate, data, sz))
+                       return -1;
+               break;
+       case CACHE_EXT_UNTRACKED:
+               istate->untracked = read_untracked_extension(data, sz);
+               break;
        default:
                if (*ext < 'A' || 'Z' < *ext)
                        return error("index uses %.4s extension, which we do not understand",
@@ -1216,12 +1561,66 @@ static int read_index_extension(struct index_state *istate,
        return 0;
 }
 
+int hold_locked_index(struct lock_file *lk, int lock_flags)
+{
+       return hold_lock_file_for_update(lk, get_index_file(), lock_flags);
+}
+
 int read_index(struct index_state *istate)
 {
        return read_index_from(istate, get_index_file());
 }
 
-static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
+static struct cache_entry *cache_entry_from_ondisk(struct ondisk_cache_entry *ondisk,
+                                                  unsigned int flags,
+                                                  const char *name,
+                                                  size_t len)
+{
+       struct cache_entry *ce = xmalloc(cache_entry_size(len));
+
+       ce->ce_stat_data.sd_ctime.sec = get_be32(&ondisk->ctime.sec);
+       ce->ce_stat_data.sd_mtime.sec = get_be32(&ondisk->mtime.sec);
+       ce->ce_stat_data.sd_ctime.nsec = get_be32(&ondisk->ctime.nsec);
+       ce->ce_stat_data.sd_mtime.nsec = get_be32(&ondisk->mtime.nsec);
+       ce->ce_stat_data.sd_dev   = get_be32(&ondisk->dev);
+       ce->ce_stat_data.sd_ino   = get_be32(&ondisk->ino);
+       ce->ce_mode  = get_be32(&ondisk->mode);
+       ce->ce_stat_data.sd_uid   = get_be32(&ondisk->uid);
+       ce->ce_stat_data.sd_gid   = get_be32(&ondisk->gid);
+       ce->ce_stat_data.sd_size  = get_be32(&ondisk->size);
+       ce->ce_flags = flags & ~CE_NAMEMASK;
+       ce->ce_namelen = len;
+       ce->index = 0;
+       hashcpy(ce->oid.hash, ondisk->sha1);
+       memcpy(ce->name, name, len);
+       ce->name[len] = '\0';
+       return ce;
+}
+
+/*
+ * Adjacent cache entries tend to share the leading paths, so it makes
+ * sense to only store the differences in later entries.  In the v4
+ * on-disk format of the index, each on-disk cache entry stores the
+ * number of bytes to be stripped from the end of the previous name,
+ * and the bytes to append to the result, to come up with its name.
+ */
+static unsigned long expand_name_field(struct strbuf *name, const char *cp_)
+{
+       const unsigned char *ep, *cp = (const unsigned char *)cp_;
+       size_t len = decode_varint(&cp);
+
+       if (name->len < len)
+               die("malformed name field in the index");
+       strbuf_remove(name, name->len - len, len);
+       for (ep = cp; *ep; ep++)
+               ; /* find the end */
+       strbuf_add(name, cp, ep - cp);
+       return (const char *)ep + 1 - cp_;
+}
+
+static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
+                                           unsigned long *ent_size,
+                                           struct strbuf *previous_name)
 {
        struct cache_entry *ce;
        size_t len;
@@ -1229,14 +1628,14 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
        unsigned int flags;
 
        /* On-disk flags are just 16 bits */
-       flags = ntohs(ondisk->flags);
+       flags = get_be16(&ondisk->flags);
        len = flags & CE_NAMEMASK;
 
        if (flags & CE_EXTENDED) {
                struct ondisk_cache_entry_extended *ondisk2;
                int extended_flags;
                ondisk2 = (struct ondisk_cache_entry_extended *)ondisk;
-               extended_flags = ntohs(ondisk2->flags2) << 16;
+               extended_flags = get_be16(&ondisk2->flags2) << 16;
                /* We do not yet understand any bit out of CE_EXTENDED_FLAGS */
                if (extended_flags & ~CE_EXTENDED_FLAGS)
                        die("Unknown index entry format %08x", extended_flags);
@@ -1246,32 +1645,88 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
        else
                name = ondisk->name;
 
-       if (len == CE_NAMEMASK)
-               len = strlen(name);
+       if (!previous_name) {
+               /* v3 and earlier */
+               if (len == CE_NAMEMASK)
+                       len = strlen(name);
+               ce = cache_entry_from_ondisk(ondisk, flags, name, len);
+
+               *ent_size = ondisk_ce_size(ce);
+       } else {
+               unsigned long consumed;
+               consumed = expand_name_field(previous_name, name);
+               ce = cache_entry_from_ondisk(ondisk, flags,
+                                            previous_name->buf,
+                                            previous_name->len);
+
+               *ent_size = (name - ((char *)ondisk)) + consumed;
+       }
+       return ce;
+}
 
-       ce = xmalloc(cache_entry_size(len));
+static void check_ce_order(struct index_state *istate)
+{
+       unsigned int i;
+
+       for (i = 1; i < istate->cache_nr; i++) {
+               struct cache_entry *ce = istate->cache[i - 1];
+               struct cache_entry *next_ce = istate->cache[i];
+               int name_compare = strcmp(ce->name, next_ce->name);
+
+               if (0 < name_compare)
+                       die("unordered stage entries in index");
+               if (!name_compare) {
+                       if (!ce_stage(ce))
+                               die("multiple stage entries for merged file '%s'",
+                                   ce->name);
+                       if (ce_stage(ce) > ce_stage(next_ce))
+                               die("unordered stage entries for '%s'",
+                                   ce->name);
+               }
+       }
+}
 
-       ce->ce_ctime.sec = ntohl(ondisk->ctime.sec);
-       ce->ce_mtime.sec = ntohl(ondisk->mtime.sec);
-       ce->ce_ctime.nsec = ntohl(ondisk->ctime.nsec);
-       ce->ce_mtime.nsec = ntohl(ondisk->mtime.nsec);
-       ce->ce_dev   = ntohl(ondisk->dev);
-       ce->ce_ino   = ntohl(ondisk->ino);
-       ce->ce_mode  = ntohl(ondisk->mode);
-       ce->ce_uid   = ntohl(ondisk->uid);
-       ce->ce_gid   = ntohl(ondisk->gid);
-       ce->ce_size  = ntohl(ondisk->size);
-       ce->ce_flags = flags;
+static void tweak_untracked_cache(struct index_state *istate)
+{
+       switch (git_config_get_untracked_cache()) {
+       case -1: /* keep: do nothing */
+               break;
+       case 0: /* false */
+               remove_untracked_cache(istate);
+               break;
+       case 1: /* true */
+               add_untracked_cache(istate);
+               break;
+       default: /* unknown value: do nothing */
+               break;
+       }
+}
 
-       hashcpy(ce->sha1, ondisk->sha1);
+static void tweak_split_index(struct index_state *istate)
+{
+       switch (git_config_get_split_index()) {
+       case -1: /* unset: do nothing */
+               break;
+       case 0: /* false */
+               remove_split_index(istate);
+               break;
+       case 1: /* true */
+               add_split_index(istate);
+               break;
+       default: /* unknown value: do nothing */
+               break;
+       }
+}
 
-       memcpy(ce->name, name, len);
-       ce->name[len] = '\0';
-       return ce;
+static void post_read_index_from(struct index_state *istate)
+{
+       check_ce_order(istate);
+       tweak_untracked_cache(istate);
+       tweak_split_index(istate);
 }
 
 /* remember to discard_cache() before reading a different cache! */
-int read_index_from(struct index_state *istate, const char *path)
+int do_read_index(struct index_state *istate, const char *path, int must_exist)
 {
        int fd, i;
        struct stat st;
@@ -1279,54 +1734,61 @@ int read_index_from(struct index_state *istate, const char *path)
        struct cache_header *hdr;
        void *mmap;
        size_t mmap_size;
+       struct strbuf previous_name_buf = STRBUF_INIT, *previous_name;
 
-       errno = EBUSY;
        if (istate->initialized)
                return istate->cache_nr;
 
-       errno = ENOENT;
        istate->timestamp.sec = 0;
        istate->timestamp.nsec = 0;
        fd = open(path, O_RDONLY);
        if (fd < 0) {
-               if (errno == ENOENT)
+               if (!must_exist && errno == ENOENT)
                        return 0;
-               die_errno("index file open failed");
+               die_errno("%s: index file open failed", path);
        }
 
        if (fstat(fd, &st))
                die_errno("cannot stat the open index");
 
-       errno = EINVAL;
        mmap_size = xsize_t(st.st_size);
        if (mmap_size < sizeof(struct cache_header) + 20)
                die("index file smaller than expected");
 
-       mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-       close(fd);
+       mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE, fd, 0);
        if (mmap == MAP_FAILED)
                die_errno("unable to map index file");
+       close(fd);
 
        hdr = mmap;
        if (verify_hdr(hdr, mmap_size) < 0)
                goto unmap;
 
+       hashcpy(istate->sha1, (const unsigned char *)hdr + mmap_size - 20);
+       istate->version = ntohl(hdr->hdr_version);
        istate->cache_nr = ntohl(hdr->hdr_entries);
        istate->cache_alloc = alloc_nr(istate->cache_nr);
-       istate->cache = xcalloc(istate->cache_alloc, sizeof(struct cache_entry *));
+       istate->cache = xcalloc(istate->cache_alloc, sizeof(*istate->cache));
        istate->initialized = 1;
 
+       if (istate->version == 4)
+               previous_name = &previous_name_buf;
+       else
+               previous_name = NULL;
+
        src_offset = sizeof(*hdr);
        for (i = 0; i < istate->cache_nr; i++) {
                struct ondisk_cache_entry *disk_ce;
                struct cache_entry *ce;
+               unsigned long consumed;
 
                disk_ce = (struct ondisk_cache_entry *)((char *)mmap + src_offset);
-               ce = create_from_disk(disk_ce);
+               ce = create_from_disk(disk_ce, &consumed, previous_name);
                set_index_entry(istate, i, ce);
 
-               src_offset += ondisk_ce_size(ce);
+               src_offset += consumed;
        }
+       strbuf_release(&previous_name_buf);
        istate->timestamp.sec = st.st_mtime;
        istate->timestamp.nsec = ST_MTIME_NSEC(st);
 
@@ -1353,10 +1815,61 @@ int read_index_from(struct index_state *istate, const char *path)
 
 unmap:
        munmap(mmap, mmap_size);
-       errno = EINVAL;
        die("index file corrupt");
 }
 
+/*
+ * Signal that the shared index is used by updating its mtime.
+ *
+ * This way, shared index can be removed if they have not been used
+ * for some time.
+ */
+static void freshen_shared_index(char *base_sha1_hex, int warn)
+{
+       char *shared_index = git_pathdup("sharedindex.%s", base_sha1_hex);
+       if (!check_and_freshen_file(shared_index, 1) && warn)
+               warning("could not freshen shared index '%s'", shared_index);
+       free(shared_index);
+}
+
+int read_index_from(struct index_state *istate, const char *path)
+{
+       struct split_index *split_index;
+       int ret;
+       char *base_sha1_hex;
+       const char *base_path;
+
+       /* istate->initialized covers both .git/index and .git/sharedindex.xxx */
+       if (istate->initialized)
+               return istate->cache_nr;
+
+       ret = do_read_index(istate, path, 0);
+
+       split_index = istate->split_index;
+       if (!split_index || is_null_sha1(split_index->base_sha1)) {
+               post_read_index_from(istate);
+               return ret;
+       }
+
+       if (split_index->base)
+               discard_index(split_index->base);
+       else
+               split_index->base = xcalloc(1, sizeof(*split_index->base));
+
+       base_sha1_hex = sha1_to_hex(split_index->base_sha1);
+       base_path = git_path("sharedindex.%s", base_sha1_hex);
+       ret = do_read_index(split_index->base, base_path, 1);
+       if (hashcmp(split_index->base_sha1, split_index->base->sha1))
+               die("broken index, expect %s in %s, got %s",
+                   base_sha1_hex, base_path,
+                   sha1_to_hex(split_index->base->sha1));
+
+       freshen_shared_index(base_sha1_hex, 0);
+       merge_base_index(istate);
+       post_read_index_from(istate);
+       return ret;
+}
+
 int is_index_unborn(struct index_state *istate)
 {
        return (!istate->cache_nr && !istate->timestamp.sec);
@@ -1366,19 +1879,28 @@ int discard_index(struct index_state *istate)
 {
        int i;
 
-       for (i = 0; i < istate->cache_nr; i++)
+       for (i = 0; i < istate->cache_nr; i++) {
+               if (istate->cache[i]->index &&
+                   istate->split_index &&
+                   istate->split_index->base &&
+                   istate->cache[i]->index <= istate->split_index->base->cache_nr &&
+                   istate->cache[i] == istate->split_index->base->cache[istate->cache[i]->index - 1])
+                       continue;
                free(istate->cache[i]);
+       }
        resolve_undo_clear_index(istate);
        istate->cache_nr = 0;
        istate->cache_changed = 0;
        istate->timestamp.sec = 0;
        istate->timestamp.nsec = 0;
-       istate->name_hash_initialized = 0;
-       free_hash(&istate->name_hash);
+       free_name_hash(istate);
        cache_tree_free(&(istate->cache_tree));
        istate->initialized = 0;
-
-       /* no need to throw away allocated active_cache */
+       FREE_AND_NULL(istate->cache);
+       istate->cache_alloc = 0;
+       discard_split_index(istate);
+       free_untracked_cache(istate->untracked);
+       istate->untracked = NULL;
        return 0;
 }
 
@@ -1401,7 +1923,7 @@ static int ce_write_flush(git_SHA_CTX *context, int fd)
        unsigned int buffered = write_buffer_len;
        if (buffered) {
                git_SHA1_Update(context, write_buffer, buffered);
-               if (write_in_full(fd, write_buffer, buffered) != buffered)
+               if (write_in_full(fd, write_buffer, buffered) < 0)
                        return -1;
                write_buffer_len = 0;
        }
@@ -1439,7 +1961,7 @@ static int write_index_ext_header(git_SHA_CTX *context, int fd,
                (ce_write(context, fd, &sz, 4) < 0)) ? -1 : 0;
 }
 
-static int ce_flush(git_SHA_CTX *context, int fd)
+static int ce_flush(git_SHA_CTX *context, int fd, unsigned char *sha1)
 {
        unsigned int left = write_buffer_len;
 
@@ -1450,15 +1972,16 @@ static int ce_flush(git_SHA_CTX *context, int fd)
 
        /* Flush first if not enough space for SHA1 signature */
        if (left + 20 > WRITE_BUFFER_SIZE) {
-               if (write_in_full(fd, write_buffer, left) != left)
+               if (write_in_full(fd, write_buffer, left) < 0)
                        return -1;
                left = 0;
        }
 
        /* Append the SHA1 signature at the end */
        git_SHA1_Final(write_buffer + left, context);
+       hashcpy(sha1, write_buffer + left);
        left += 20;
-       return (write_in_full(fd, write_buffer, left) != left) ? -1 : 0;
+       return (write_in_full(fd, write_buffer, left) < 0) ? -1 : 0;
 }
 
 static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
@@ -1467,7 +1990,7 @@ static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
         * The only thing we care about in this function is to smudge the
         * falsely clean entry due to touch-update-touch race, so we leave
         * everything else as they are.  We are called for entries whose
-        * ce_mtime match the index file mtime.
+        * ce_stat_data.sd_mtime match the index file mtime.
         *
         * Note that this actually does not do much for gitlinks, for
         * which ce_match_stat_basic() always goes to the actual
@@ -1506,44 +2029,140 @@ static void ce_smudge_racily_clean_entry(struct cache_entry *ce)
                 * file, and never calls us, so the cached size information
                 * for "frotz" stays 6 which does not match the filesystem.
                 */
-               ce->ce_size = 0;
+               ce->ce_stat_data.sd_size = 0;
        }
 }
 
-static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce)
+/* Copy miscellaneous fields but not the name */
+static void copy_cache_entry_to_ondisk(struct ondisk_cache_entry *ondisk,
+                                      struct cache_entry *ce)
 {
-       int size = ondisk_ce_size(ce);
-       struct ondisk_cache_entry *ondisk = xcalloc(1, size);
-       char *name;
-       int result;
-
-       ondisk->ctime.sec = htonl(ce->ce_ctime.sec);
-       ondisk->mtime.sec = htonl(ce->ce_mtime.sec);
-       ondisk->ctime.nsec = htonl(ce->ce_ctime.nsec);
-       ondisk->mtime.nsec = htonl(ce->ce_mtime.nsec);
-       ondisk->dev  = htonl(ce->ce_dev);
-       ondisk->ino  = htonl(ce->ce_ino);
+       short flags;
+
+       ondisk->ctime.sec = htonl(ce->ce_stat_data.sd_ctime.sec);
+       ondisk->mtime.sec = htonl(ce->ce_stat_data.sd_mtime.sec);
+       ondisk->ctime.nsec = htonl(ce->ce_stat_data.sd_ctime.nsec);
+       ondisk->mtime.nsec = htonl(ce->ce_stat_data.sd_mtime.nsec);
+       ondisk->dev  = htonl(ce->ce_stat_data.sd_dev);
+       ondisk->ino  = htonl(ce->ce_stat_data.sd_ino);
        ondisk->mode = htonl(ce->ce_mode);
-       ondisk->uid  = htonl(ce->ce_uid);
-       ondisk->gid  = htonl(ce->ce_gid);
-       ondisk->size = htonl(ce->ce_size);
-       hashcpy(ondisk->sha1, ce->sha1);
-       ondisk->flags = htons(ce->ce_flags);
+       ondisk->uid  = htonl(ce->ce_stat_data.sd_uid);
+       ondisk->gid  = htonl(ce->ce_stat_data.sd_gid);
+       ondisk->size = htonl(ce->ce_stat_data.sd_size);
+       hashcpy(ondisk->sha1, ce->oid.hash);
+
+       flags = ce->ce_flags & ~CE_NAMEMASK;
+       flags |= (ce_namelen(ce) >= CE_NAMEMASK ? CE_NAMEMASK : ce_namelen(ce));
+       ondisk->flags = htons(flags);
        if (ce->ce_flags & CE_EXTENDED) {
                struct ondisk_cache_entry_extended *ondisk2;
                ondisk2 = (struct ondisk_cache_entry_extended *)ondisk;
                ondisk2->flags2 = htons((ce->ce_flags & CE_EXTENDED_FLAGS) >> 16);
-               name = ondisk2->name;
        }
+}
+
+static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce,
+                         struct strbuf *previous_name, struct ondisk_cache_entry *ondisk)
+{
+       int size;
+       int saved_namelen = saved_namelen; /* compiler workaround */
+       int result;
+       static unsigned char padding[8] = { 0x00 };
+
+       if (ce->ce_flags & CE_STRIP_NAME) {
+               saved_namelen = ce_namelen(ce);
+               ce->ce_namelen = 0;
+       }
+
+       if (ce->ce_flags & CE_EXTENDED)
+               size = offsetof(struct ondisk_cache_entry_extended, name);
        else
-               name = ondisk->name;
-       memcpy(name, ce->name, ce_namelen(ce));
+               size = offsetof(struct ondisk_cache_entry, name);
+
+       if (!previous_name) {
+               int len = ce_namelen(ce);
+               copy_cache_entry_to_ondisk(ondisk, ce);
+               result = ce_write(c, fd, ondisk, size);
+               if (!result)
+                       result = ce_write(c, fd, ce->name, len);
+               if (!result)
+                       result = ce_write(c, fd, padding, align_padding_size(size, len));
+       } else {
+               int common, to_remove, prefix_size;
+               unsigned char to_remove_vi[16];
+               for (common = 0;
+                    (ce->name[common] &&
+                     common < previous_name->len &&
+                     ce->name[common] == previous_name->buf[common]);
+                    common++)
+                       ; /* still matching */
+               to_remove = previous_name->len - common;
+               prefix_size = encode_varint(to_remove, to_remove_vi);
+
+               copy_cache_entry_to_ondisk(ondisk, ce);
+               result = ce_write(c, fd, ondisk, size);
+               if (!result)
+                       result = ce_write(c, fd, to_remove_vi, prefix_size);
+               if (!result)
+                       result = ce_write(c, fd, ce->name + common, ce_namelen(ce) - common);
+               if (!result)
+                       result = ce_write(c, fd, padding, 1);
+
+               strbuf_splice(previous_name, common, to_remove,
+                             ce->name + common, ce_namelen(ce) - common);
+       }
+       if (ce->ce_flags & CE_STRIP_NAME) {
+               ce->ce_namelen = saved_namelen;
+               ce->ce_flags &= ~CE_STRIP_NAME;
+       }
 
-       result = ce_write(c, fd, ondisk, size);
-       free(ondisk);
        return result;
 }
 
+/*
+ * This function verifies if index_state has the correct sha1 of the
+ * index file.  Don't die if we have any other failure, just return 0.
+ */
+static int verify_index_from(const struct index_state *istate, const char *path)
+{
+       int fd;
+       ssize_t n;
+       struct stat st;
+       unsigned char sha1[20];
+
+       if (!istate->initialized)
+               return 0;
+
+       fd = open(path, O_RDONLY);
+       if (fd < 0)
+               return 0;
+
+       if (fstat(fd, &st))
+               goto out;
+
+       if (st.st_size < sizeof(struct cache_header) + 20)
+               goto out;
+
+       n = pread_in_full(fd, sha1, 20, st.st_size - 20);
+       if (n != 20)
+               goto out;
+
+       if (hashcmp(istate->sha1, sha1))
+               goto out;
+
+       close(fd);
+       return 1;
+
+out:
+       close(fd);
+       return 0;
+}
+
+static int verify_index(const struct index_state *istate)
+{
+       return verify_index_from(istate, get_index_file());
+}
+
 static int has_racy_timestamp(struct index_state *istate)
 {
        int entries = istate->cache_nr;
@@ -1558,25 +2177,29 @@ static int has_racy_timestamp(struct index_state *istate)
 }
 
 /*
- * Opportunisticly update the index but do not complain if we can't
+ * Opportunistically update the index but do not complain if we can't
  */
 void update_index_if_able(struct index_state *istate, struct lock_file *lockfile)
 {
        if ((istate->cache_changed || has_racy_timestamp(istate)) &&
-           !write_index(istate, lockfile->fd))
-               commit_locked_index(lockfile);
-       else
+           verify_index(istate) &&
+           write_locked_index(istate, lockfile, COMMIT_LOCK))
                rollback_lock_file(lockfile);
 }
 
-int write_index(struct index_state *istate, int newfd)
+static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
+                         int strip_extensions)
 {
+       int newfd = tempfile->fd;
        git_SHA_CTX c;
        struct cache_header hdr;
-       int i, err, removed, extended;
+       int i, err = 0, removed, extended, hdr_version;
        struct cache_entry **cache = istate->cache;
        int entries = istate->cache_nr;
        struct stat st;
+       struct ondisk_cache_entry_extended ondisk;
+       struct strbuf previous_name_buf = STRBUF_INIT, *previous_name;
+       int drop_cache_tree = 0;
 
        for (i = removed = extended = 0; i < entries; i++) {
                if (cache[i]->ce_flags & CE_REMOVE)
@@ -1590,27 +2213,71 @@ int write_index(struct index_state *istate, int newfd)
                }
        }
 
+       if (!istate->version) {
+               istate->version = get_index_format_default();
+               if (getenv("GIT_TEST_SPLIT_INDEX"))
+                       init_split_index(istate);
+       }
+
+       /* demote version 3 to version 2 when the latter suffices */
+       if (istate->version == 3 || istate->version == 2)
+               istate->version = extended ? 3 : 2;
+
+       hdr_version = istate->version;
+
        hdr.hdr_signature = htonl(CACHE_SIGNATURE);
-       /* for extended format, increase version so older git won't try to read it */
-       hdr.hdr_version = htonl(extended ? 3 : 2);
+       hdr.hdr_version = htonl(hdr_version);
        hdr.hdr_entries = htonl(entries - removed);
 
        git_SHA1_Init(&c);
        if (ce_write(&c, newfd, &hdr, sizeof(hdr)) < 0)
                return -1;
 
+       previous_name = (hdr_version == 4) ? &previous_name_buf : NULL;
+
        for (i = 0; i < entries; i++) {
                struct cache_entry *ce = cache[i];
                if (ce->ce_flags & CE_REMOVE)
                        continue;
                if (!ce_uptodate(ce) && is_racy_timestamp(istate, ce))
                        ce_smudge_racily_clean_entry(ce);
-               if (ce_write_entry(&c, newfd, ce) < 0)
-                       return -1;
+               if (is_null_oid(&ce->oid)) {
+                       static const char msg[] = "cache entry has null sha1: %s";
+                       static int allow = -1;
+
+                       if (allow < 0)
+                               allow = git_env_bool("GIT_ALLOW_NULL_SHA1", 0);
+                       if (allow)
+                               warning(msg, ce->name);
+                       else
+                               err = error(msg, ce->name);
+
+                       drop_cache_tree = 1;
+               }
+               if (ce_write_entry(&c, newfd, ce, previous_name, (struct ondisk_cache_entry *)&ondisk) < 0)
+                       err = -1;
+
+               if (err)
+                       break;
        }
+       strbuf_release(&previous_name_buf);
+
+       if (err)
+               return err;
 
        /* Write extension data here */
-       if (istate->cache_tree) {
+       if (!strip_extensions && istate->split_index) {
+               struct strbuf sb = STRBUF_INIT;
+
+               err = write_link_extension(&sb, istate) < 0 ||
+                       write_index_ext_header(&c, newfd, CACHE_EXT_LINK,
+                                              sb.len) < 0 ||
+                       ce_write(&c, newfd, sb.buf, sb.len) < 0;
+               strbuf_release(&sb);
+               if (err)
+                       return -1;
+       }
+       if (!strip_extensions && !drop_cache_tree && istate->cache_tree) {
                struct strbuf sb = STRBUF_INIT;
 
                cache_tree_write(&sb, istate->cache_tree);
@@ -1620,7 +2287,7 @@ int write_index(struct index_state *istate, int newfd)
                if (err)
                        return -1;
        }
-       if (istate->resolve_undo) {
+       if (!strip_extensions && istate->resolve_undo) {
                struct strbuf sb = STRBUF_INIT;
 
                resolve_undo_write(&sb, istate->resolve_undo);
@@ -1631,14 +2298,235 @@ int write_index(struct index_state *istate, int newfd)
                if (err)
                        return -1;
        }
+       if (!strip_extensions && istate->untracked) {
+               struct strbuf sb = STRBUF_INIT;
 
-       if (ce_flush(&c, newfd) || fstat(newfd, &st))
+               write_untracked_extension(&sb, istate->untracked);
+               err = write_index_ext_header(&c, newfd, CACHE_EXT_UNTRACKED,
+                                            sb.len) < 0 ||
+                       ce_write(&c, newfd, sb.buf, sb.len) < 0;
+               strbuf_release(&sb);
+               if (err)
+                       return -1;
+       }
+
+       if (ce_flush(&c, newfd, istate->sha1))
+               return -1;
+       if (close_tempfile_gently(tempfile)) {
+               error(_("could not close '%s'"), tempfile->filename.buf);
+               delete_tempfile(&tempfile);
+               return -1;
+       }
+       if (stat(tempfile->filename.buf, &st))
                return -1;
        istate->timestamp.sec = (unsigned int)st.st_mtime;
        istate->timestamp.nsec = ST_MTIME_NSEC(st);
        return 0;
 }
 
+void set_alternate_index_output(const char *name)
+{
+       alternate_index_output = name;
+}
+
+static int commit_locked_index(struct lock_file *lk)
+{
+       if (alternate_index_output)
+               return commit_lock_file_to(lk, alternate_index_output);
+       else
+               return commit_lock_file(lk);
+}
+
+static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
+                                unsigned flags)
+{
+       int ret = do_write_index(istate, lock->tempfile, 0);
+       if (ret)
+               return ret;
+       assert((flags & (COMMIT_LOCK | CLOSE_LOCK)) !=
+              (COMMIT_LOCK | CLOSE_LOCK));
+       if (flags & COMMIT_LOCK)
+               return commit_locked_index(lock);
+       else if (flags & CLOSE_LOCK)
+               return close_lock_file_gently(lock);
+       else
+               return ret;
+}
+
+static int write_split_index(struct index_state *istate,
+                            struct lock_file *lock,
+                            unsigned flags)
+{
+       int ret;
+       prepare_to_write_split_index(istate);
+       ret = do_write_locked_index(istate, lock, flags);
+       finish_writing_split_index(istate);
+       return ret;
+}
+
+static const char *shared_index_expire = "2.weeks.ago";
+
+static unsigned long get_shared_index_expire_date(void)
+{
+       static unsigned long shared_index_expire_date;
+       static int shared_index_expire_date_prepared;
+
+       if (!shared_index_expire_date_prepared) {
+               git_config_get_expiry("splitindex.sharedindexexpire",
+                                     &shared_index_expire);
+               shared_index_expire_date = approxidate(shared_index_expire);
+               shared_index_expire_date_prepared = 1;
+       }
+
+       return shared_index_expire_date;
+}
+
+static int should_delete_shared_index(const char *shared_index_path)
+{
+       struct stat st;
+       unsigned long expiration;
+
+       /* Check timestamp */
+       expiration = get_shared_index_expire_date();
+       if (!expiration)
+               return 0;
+       if (stat(shared_index_path, &st))
+               return error_errno(_("could not stat '%s'"), shared_index_path);
+       if (st.st_mtime > expiration)
+               return 0;
+
+       return 1;
+}
+
+static int clean_shared_index_files(const char *current_hex)
+{
+       struct dirent *de;
+       DIR *dir = opendir(get_git_dir());
+
+       if (!dir)
+               return error_errno(_("unable to open git dir: %s"), get_git_dir());
+
+       while ((de = readdir(dir)) != NULL) {
+               const char *sha1_hex;
+               const char *shared_index_path;
+               if (!skip_prefix(de->d_name, "sharedindex.", &sha1_hex))
+                       continue;
+               if (!strcmp(sha1_hex, current_hex))
+                       continue;
+               shared_index_path = git_path("%s", de->d_name);
+               if (should_delete_shared_index(shared_index_path) > 0 &&
+                   unlink(shared_index_path))
+                       warning_errno(_("unable to unlink: %s"), shared_index_path);
+       }
+       closedir(dir);
+
+       return 0;
+}
+
+static int write_shared_index(struct index_state *istate,
+                             struct lock_file *lock, unsigned flags)
+{
+       struct tempfile *temp;
+       struct split_index *si = istate->split_index;
+       int ret;
+
+       temp = mks_tempfile(git_path("sharedindex_XXXXXX"));
+       if (!temp) {
+               hashclr(si->base_sha1);
+               return do_write_locked_index(istate, lock, flags);
+       }
+       move_cache_to_base_index(istate);
+       ret = do_write_index(si->base, temp, 1);
+       if (ret) {
+               delete_tempfile(&temp);
+               return ret;
+       }
+       ret = adjust_shared_perm(get_tempfile_path(temp));
+       if (ret) {
+               int save_errno = errno;
+               error("cannot fix permission bits on %s", get_tempfile_path(temp));
+               delete_tempfile(&temp);
+               errno = save_errno;
+               return ret;
+       }
+       ret = rename_tempfile(&temp,
+                             git_path("sharedindex.%s", sha1_to_hex(si->base->sha1)));
+       if (!ret) {
+               hashcpy(si->base_sha1, si->base->sha1);
+               clean_shared_index_files(sha1_to_hex(si->base->sha1));
+       }
+
+       return ret;
+}
+
+static const int default_max_percent_split_change = 20;
+
+static int too_many_not_shared_entries(struct index_state *istate)
+{
+       int i, not_shared = 0;
+       int max_split = git_config_get_max_percent_split_change();
+
+       switch (max_split) {
+       case -1:
+               /* not or badly configured: use the default value */
+               max_split = default_max_percent_split_change;
+               break;
+       case 0:
+               return 1; /* 0% means always write a new shared index */
+       case 100:
+               return 0; /* 100% means never write a new shared index */
+       default:
+               break; /* just use the configured value */
+       }
+
+       /* Count not shared entries */
+       for (i = 0; i < istate->cache_nr; i++) {
+               struct cache_entry *ce = istate->cache[i];
+               if (!ce->index)
+                       not_shared++;
+       }
+
+       return (int64_t)istate->cache_nr * max_split < (int64_t)not_shared * 100;
+}
+
+int write_locked_index(struct index_state *istate, struct lock_file *lock,
+                      unsigned flags)
+{
+       int new_shared_index, ret;
+       struct split_index *si = istate->split_index;
+
+       if (!si || alternate_index_output ||
+           (istate->cache_changed & ~EXTMASK)) {
+               if (si)
+                       hashclr(si->base_sha1);
+               return do_write_locked_index(istate, lock, flags);
+       }
+
+       if (getenv("GIT_TEST_SPLIT_INDEX")) {
+               int v = si->base_sha1[0];
+               if ((v & 15) < 6)
+                       istate->cache_changed |= SPLIT_INDEX_ORDERED;
+       }
+       if (too_many_not_shared_entries(istate))
+               istate->cache_changed |= SPLIT_INDEX_ORDERED;
+
+       new_shared_index = istate->cache_changed & SPLIT_INDEX_ORDERED;
+
+       if (new_shared_index) {
+               ret = write_shared_index(istate, lock, flags);
+               if (ret)
+                       return ret;
+       }
+
+       ret = write_split_index(istate, lock, flags);
+
+       /* Freshen the shared index only if the split-index was written */
+       if (!ret && !new_shared_index)
+               freshen_shared_index(sha1_to_hex(si->base_sha1), 1);
+
+       return ret;
+}
+
 /*
  * Read the index file that is potentially unmerged into given
  * index_state, dropping any unmerged entries.  Returns true if
@@ -1660,16 +2548,16 @@ int read_index_unmerged(struct index_state *istate)
                if (!ce_stage(ce))
                        continue;
                unmerged = 1;
-               len = strlen(ce->name);
+               len = ce_namelen(ce);
                size = cache_entry_size(len);
                new_ce = xcalloc(1, size);
                memcpy(new_ce->name, ce->name, len);
-               new_ce->ce_flags = create_ce_flags(len, 0) | CE_CONFLICTED;
+               new_ce->ce_flags = create_ce_flags(0) | CE_CONFLICTED;
+               new_ce->ce_namelen = len;
                new_ce->ce_mode = ce->ce_mode;
                if (add_index_entry(istate, new_ce, 0))
                        return error("%s: cannot drop to stage #0",
-                                    ce->name);
-               i = index_name_pos(istate, new_ce->name, len);
+                                    new_ce->name);
        }
        return unmerged;
 }
@@ -1701,3 +2589,73 @@ int index_name_is_other(const struct index_state *istate, const char *name,
        }
        return 1;
 }
+
+void *read_blob_data_from_index(const struct index_state *istate,
+                               const char *path, unsigned long *size)
+{
+       int pos, len;
+       unsigned long sz;
+       enum object_type type;
+       void *data;
+
+       len = strlen(path);
+       pos = index_name_pos(istate, path, len);
+       if (pos < 0) {
+               /*
+                * We might be in the middle of a merge, in which
+                * case we would read stage #2 (ours).
+                */
+               int i;
+               for (i = -pos - 1;
+                    (pos < 0 && i < istate->cache_nr &&
+                     !strcmp(istate->cache[i]->name, path));
+                    i++)
+                       if (ce_stage(istate->cache[i]) == 2)
+                               pos = i;
+       }
+       if (pos < 0)
+               return NULL;
+       data = read_sha1_file(istate->cache[pos]->oid.hash, &type, &sz);
+       if (!data || type != OBJ_BLOB) {
+               free(data);
+               return NULL;
+       }
+       if (size)
+               *size = sz;
+       return data;
+}
+
+void stat_validity_clear(struct stat_validity *sv)
+{
+       FREE_AND_NULL(sv->sd);
+}
+
+int stat_validity_check(struct stat_validity *sv, const char *path)
+{
+       struct stat st;
+
+       if (stat(path, &st) < 0)
+               return sv->sd == NULL;
+       if (!sv->sd)
+               return 0;
+       return S_ISREG(st.st_mode) && !match_stat_data(sv->sd, &st);
+}
+
+void stat_validity_update(struct stat_validity *sv, int fd)
+{
+       struct stat st;
+
+       if (fstat(fd, &st) < 0 || !S_ISREG(st.st_mode))
+               stat_validity_clear(sv);
+       else {
+               if (!sv->sd)
+                       sv->sd = xcalloc(1, sizeof(struct stat_data));
+               fill_stat_data(sv->sd, &st);
+       }
+}
+
+void move_index_extensions(struct index_state *dst, struct index_state *src)
+{
+       dst->untracked = src->untracked;
+       src->untracked = NULL;
+}