graph.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "commit.h"
   4 #include "color.h"
   5 #include "graph.h"
   6 #include "revision.h"
   7 #include "argv-array.h"
   8
   9 /* Internal API */
  10
  11 /*
  12  * Output a padding line in the graph.
  13  * This is similar to graph_next_line().  However, it is guaranteed to
  14  * never print the current commit line.  Instead, if the commit line is
  15  * next, it will simply output a line of vertical padding, extending the
  16  * branch lines downwards, but leaving them otherwise unchanged.
  17  */
  18 static void graph_padding_line(struct git_graph *graph, struct strbuf *sb);
  19
  20 /*
  21  * Print a strbuf.  If the graph is non-NULL, all lines but the first will be
  22  * prefixed with the graph output.
  23  *
  24  * If the strbuf ends with a newline, the output will end after this
  25  * newline.  A new graph line will not be printed after the final newline.
  26  * If the strbuf is empty, no output will be printed.
  27  *
  28  * Since the first line will not include the graph output, the caller is
  29  * responsible for printing this line's graph (perhaps via
  30  * graph_show_commit() or graph_show_oneline()) before calling
  31  * graph_show_strbuf().
  32  *
  33  * Note that unlike some other graph display functions, you must pass the file
  34  * handle directly. It is assumed that this is the same file handle as the
  35  * file specified by the graph diff options. This is necessary so that
  36  * graph_show_strbuf can be called even with a NULL graph.
  37  */
  38 static void graph_show_strbuf(struct git_graph *graph,
  39                               FILE *file,
  40                               struct strbuf const *sb);
  41
  42 /*
  43  * TODO:
  44  * - Limit the number of columns, similar to the way gitk does.
  45  *   If we reach more than a specified number of columns, omit
  46  *   sections of some columns.
  47  */
  48
  49 struct column {
  50         /*
  51          * The parent commit of this column.
  52          */
  53         struct commit *commit;
  54         /*
  55          * The color to (optionally) print this column in.  This is an
  56          * index into column_colors.
  57          */
  58         unsigned short color;
  59 };
  60
  61 enum graph_state {
  62         GRAPH_PADDING,
  63         GRAPH_SKIP,
  64         GRAPH_PRE_COMMIT,
  65         GRAPH_COMMIT,
  66         GRAPH_POST_MERGE,
  67         GRAPH_COLLAPSING
  68 };
  69
  70 static void graph_show_line_prefix(const struct diff_options *diffopt)
  71 {
  72         if (!diffopt || !diffopt->line_prefix)
  73                 return;
  74
  75         fwrite(diffopt->line_prefix,
  76                sizeof(char),
  77                diffopt->line_prefix_length,
  78                diffopt->file);
  79 }
  80
  81 static const char **column_colors;
  82 static unsigned short column_colors_max;
  83
  84 static void parse_graph_colors_config(struct argv_array *colors, const char *string)
  85 {
  86         const char *end, *start;
  87
  88         start = string;
  89         end = string + strlen(string);
  90         while (start < end) {
  91                 const char *comma = strchrnul(start, ',');
  92                 char color[COLOR_MAXLEN];
  93
  94                 if (!color_parse_mem(start, comma - start, color))
  95                         argv_array_push(colors, color);
  96                 else
  97                         warning(_("ignore invalid color '%.*s' in log.graphColors"),
  98                                 (int)(comma - start), start);
  99                 start = comma + 1;
 100         }
 101         argv_array_push(colors, GIT_COLOR_RESET);
 102 }
 103
 104 void graph_set_column_colors(const char **colors, unsigned short colors_max)
 105 {
 106         column_colors = colors;
 107         column_colors_max = colors_max;
 108 }
 109
 110 static const char *column_get_color_code(unsigned short color)
 111 {
 112         return column_colors[color];
 113 }
 114
 115 static void strbuf_write_column(struct strbuf *sb, const struct column *c,
 116                                 char col_char)
 117 {
 118         if (c->color < column_colors_max)
 119                 strbuf_addstr(sb, column_get_color_code(c->color));
 120         strbuf_addch(sb, col_char);
 121         if (c->color < column_colors_max)
 122                 strbuf_addstr(sb, column_get_color_code(column_colors_max));
 123 }
 124
 125 struct git_graph {
 126         /*
 127          * The commit currently being processed
 128          */
 129         struct commit *commit;
 130         /* The rev-info used for the current traversal */
 131         struct rev_info *revs;
 132         /*
 133          * The number of interesting parents that this commit has.
 134          *
 135          * Note that this is not the same as the actual number of parents.
 136          * This count excludes parents that won't be printed in the graph
 137          * output, as determined by graph_is_interesting().
 138          */
 139         int num_parents;
 140         /*
 141          * The width of the graph output for this commit.
 142          * All rows for this commit are padded to this width, so that
 143          * messages printed after the graph output are aligned.
 144          */
 145         int width;
 146         /*
 147          * The next expansion row to print
 148          * when state is GRAPH_PRE_COMMIT
 149          */
 150         int expansion_row;
 151         /*
 152          * The current output state.
 153          * This tells us what kind of line graph_next_line() should output.
 154          */
 155         enum graph_state state;
 156         /*
 157          * The output state for the previous line of output.
 158          * This is primarily used to determine how the first merge line
 159          * should appear, based on the last line of the previous commit.
 160          */
 161         enum graph_state prev_state;
 162         /*
 163          * The index of the column that refers to this commit.
 164          *
 165          * If none of the incoming columns refer to this commit,
 166          * this will be equal to num_columns.
 167          */
 168         int commit_index;
 169         /*
 170          * The commit_index for the previously displayed commit.
 171          *
 172          * This is used to determine how the first line of a merge
 173          * graph output should appear, based on the last line of the
 174          * previous commit.
 175          */
 176         int prev_commit_index;
 177         /*
 178          * The maximum number of columns that can be stored in the columns
 179          * and new_columns arrays.  This is also half the number of entries
 180          * that can be stored in the mapping and new_mapping arrays.
 181          */
 182         int column_capacity;
 183         /*
 184          * The number of columns (also called "branch lines" in some places)
 185          */
 186         int num_columns;
 187         /*
 188          * The number of columns in the new_columns array
 189          */
 190         int num_new_columns;
 191         /*
 192          * The number of entries in the mapping array
 193          */
 194         int mapping_size;
 195         /*
 196          * The column state before we output the current commit.
 197          */
 198         struct column *columns;
 199         /*
 200          * The new column state after we output the current commit.
 201          * Only valid when state is GRAPH_COLLAPSING.
 202          */
 203         struct column *new_columns;
 204         /*
 205          * An array that tracks the current state of each
 206          * character in the output line during state GRAPH_COLLAPSING.
 207          * Each entry is -1 if this character is empty, or a non-negative
 208          * integer if the character contains a branch line.  The value of
 209          * the integer indicates the target position for this branch line.
 210          * (I.e., this array maps the current column positions to their
 211          * desired positions.)
 212          *
 213          * The maximum capacity of this array is always
 214          * sizeof(int) * 2 * column_capacity.
 215          */
 216         int *mapping;
 217         /*
 218          * A temporary array for computing the next mapping state
 219          * while we are outputting a mapping line.  This is stored as part
 220          * of the git_graph simply so we don't have to allocate a new
 221          * temporary array each time we have to output a collapsing line.
 222          */
 223         int *new_mapping;
 224         /*
 225          * The current default column color being used.  This is
 226          * stored as an index into the array column_colors.
 227          */
 228         unsigned short default_column_color;
 229 };
 230
 231 static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void *data)
 232 {
 233         struct git_graph *graph = data;
 234         static struct strbuf msgbuf = STRBUF_INIT;
 235
 236         assert(opt);
 237
 238         strbuf_reset(&msgbuf);
 239         if (opt->line_prefix)
 240                 strbuf_add(&msgbuf, opt->line_prefix,
 241                            opt->line_prefix_length);
 242         if (graph)
 243                 graph_padding_line(graph, &msgbuf);
 244         return &msgbuf;
 245 }
 246
 247 static const struct diff_options *default_diffopt;
 248
 249 void graph_setup_line_prefix(struct diff_options *diffopt)
 250 {
 251         default_diffopt = diffopt;
 252
 253         /* setup an output prefix callback if necessary */
 254         if (diffopt && !diffopt->output_prefix)
 255                 diffopt->output_prefix = diff_output_prefix_callback;
 256 }
 257
 258
 259 struct git_graph *graph_init(struct rev_info *opt)
 260 {
 261         struct git_graph *graph = xmalloc(sizeof(struct git_graph));
 262
 263         if (!column_colors) {
 264                 char *string;
 265                 if (git_config_get_string("log.graphcolors", &string)) {
 266                         /* not configured -- use default */
 267                         graph_set_column_colors(column_colors_ansi,
 268                                                 column_colors_ansi_max);
 269                 } else {
 270                         static struct argv_array custom_colors = ARGV_ARRAY_INIT;
 271                         argv_array_clear(&custom_colors);
 272                         parse_graph_colors_config(&custom_colors, string);
 273                         free(string);
 274                         /* graph_set_column_colors takes a max-index, not a count */
 275                         graph_set_column_colors(custom_colors.argv,
 276                                                 custom_colors.argc - 1);
 277                 }
 278         }
 279
 280         graph->commit = NULL;
 281         graph->revs = opt;
 282         graph->num_parents = 0;
 283         graph->expansion_row = 0;
 284         graph->state = GRAPH_PADDING;
 285         graph->prev_state = GRAPH_PADDING;
 286         graph->commit_index = 0;
 287         graph->prev_commit_index = 0;
 288         graph->num_columns = 0;
 289         graph->num_new_columns = 0;
 290         graph->mapping_size = 0;
 291         /*
 292          * Start the column color at the maximum value, since we'll
 293          * always increment it for the first commit we output.
 294          * This way we start at 0 for the first commit.
 295          */
 296         graph->default_column_color = column_colors_max - 1;
 297
 298         /*
 299          * Allocate a reasonably large default number of columns
 300          * We'll automatically grow columns later if we need more room.
 301          */
 302         graph->column_capacity = 30;
 303         ALLOC_ARRAY(graph->columns, graph->column_capacity);
 304         ALLOC_ARRAY(graph->new_columns, graph->column_capacity);
 305         ALLOC_ARRAY(graph->mapping, 2 * graph->column_capacity);
 306         ALLOC_ARRAY(graph->new_mapping, 2 * graph->column_capacity);
 307
 308         /*
 309          * The diff output prefix callback, with this we can make
 310          * all the diff output to align with the graph lines.
 311          */
 312         opt->diffopt.output_prefix = diff_output_prefix_callback;
 313         opt->diffopt.output_prefix_data = graph;
 314
 315         return graph;
 316 }
 317
 318 static void graph_update_state(struct git_graph *graph, enum graph_state s)
 319 {
 320         graph->prev_state = graph->state;
 321         graph->state = s;
 322 }
 323
 324 static void graph_ensure_capacity(struct git_graph *graph, int num_columns)
 325 {
 326         if (graph->column_capacity >= num_columns)
 327                 return;
 328
 329         do {
 330                 graph->column_capacity *= 2;
 331         } while (graph->column_capacity < num_columns);
 332
 333         REALLOC_ARRAY(graph->columns, graph->column_capacity);
 334         REALLOC_ARRAY(graph->new_columns, graph->column_capacity);
 335         REALLOC_ARRAY(graph->mapping, graph->column_capacity * 2);
 336         REALLOC_ARRAY(graph->new_mapping, graph->column_capacity * 2);
 337 }
 338
 339 /*
 340  * Returns 1 if the commit will be printed in the graph output,
 341  * and 0 otherwise.
 342  */
 343 static int graph_is_interesting(struct git_graph *graph, struct commit *commit)
 344 {
 345         /*
 346          * If revs->boundary is set, commits whose children have
 347          * been shown are always interesting, even if they have the
 348          * UNINTERESTING or TREESAME flags set.
 349          */
 350         if (graph->revs && graph->revs->boundary) {
 351                 if (commit->object.flags & CHILD_SHOWN)
 352                         return 1;
 353         }
 354
 355         /*
 356          * Otherwise, use get_commit_action() to see if this commit is
 357          * interesting
 358          */
 359         return get_commit_action(graph->revs, commit) == commit_show;
 360 }
 361
 362 static struct commit_list *next_interesting_parent(struct git_graph *graph,
 363                                                    struct commit_list *orig)
 364 {
 365         struct commit_list *list;
 366
 367         /*
 368          * If revs->first_parent_only is set, only the first
 369          * parent is interesting.  None of the others are.
 370          */
 371         if (graph->revs->first_parent_only)
 372                 return NULL;
 373
 374         /*
 375          * Return the next interesting commit after orig
 376          */
 377         for (list = orig->next; list; list = list->next) {
 378                 if (graph_is_interesting(graph, list->item))
 379                         return list;
 380         }
 381
 382         return NULL;
 383 }
 384
 385 static struct commit_list *first_interesting_parent(struct git_graph *graph)
 386 {
 387         struct commit_list *parents = graph->commit->parents;
 388
 389         /*
 390          * If this commit has no parents, ignore it
 391          */
 392         if (!parents)
 393                 return NULL;
 394
 395         /*
 396          * If the first parent is interesting, return it
 397          */
 398         if (graph_is_interesting(graph, parents->item))
 399                 return parents;
 400
 401         /*
 402          * Otherwise, call next_interesting_parent() to get
 403          * the next interesting parent
 404          */
 405         return next_interesting_parent(graph, parents);
 406 }
 407
 408 static unsigned short graph_get_current_column_color(const struct git_graph *graph)
 409 {
 410         if (!want_color(graph->revs->diffopt.use_color))
 411                 return column_colors_max;
 412         return graph->default_column_color;
 413 }
 414
 415 /*
 416  * Update the graph's default column color.
 417  */
 418 static void graph_increment_column_color(struct git_graph *graph)
 419 {
 420         graph->default_column_color = (graph->default_column_color + 1) %
 421                 column_colors_max;
 422 }
 423
 424 static unsigned short graph_find_commit_color(const struct git_graph *graph,
 425                                               const struct commit *commit)
 426 {
 427         int i;
 428         for (i = 0; i < graph->num_columns; i++) {
 429                 if (graph->columns[i].commit == commit)
 430                         return graph->columns[i].color;
 431         }
 432         return graph_get_current_column_color(graph);
 433 }
 434
 435 static void graph_insert_into_new_columns(struct git_graph *graph,
 436                                           struct commit *commit,
 437                                           int *mapping_index)
 438 {
 439         int i;
 440
 441         /*
 442          * If the commit is already in the new_columns list, we don't need to
 443          * add it.  Just update the mapping correctly.
 444          */
 445         for (i = 0; i < graph->num_new_columns; i++) {
 446                 if (graph->new_columns[i].commit == commit) {
 447                         graph->mapping[*mapping_index] = i;
 448                         *mapping_index += 2;
 449                         return;
 450                 }
 451         }
 452
 453         /*
 454          * This commit isn't already in new_columns.  Add it.
 455          */
 456         graph->new_columns[graph->num_new_columns].commit = commit;
 457         graph->new_columns[graph->num_new_columns].color = graph_find_commit_color(graph, commit);
 458         graph->mapping[*mapping_index] = graph->num_new_columns;
 459         *mapping_index += 2;
 460         graph->num_new_columns++;
 461 }
 462
 463 static void graph_update_width(struct git_graph *graph,
 464                                int is_commit_in_existing_columns)
 465 {
 466         /*
 467          * Compute the width needed to display the graph for this commit.
 468          * This is the maximum width needed for any row.  All other rows
 469          * will be padded to this width.
 470          *
 471          * Compute the number of columns in the widest row:
 472          * Count each existing column (graph->num_columns), and each new
 473          * column added by this commit.
 474          */
 475         int max_cols = graph->num_columns + graph->num_parents;
 476
 477         /*
 478          * Even if the current commit has no parents to be printed, it
 479          * still takes up a column for itself.
 480          */
 481         if (graph->num_parents < 1)
 482                 max_cols++;
 483
 484         /*
 485          * We added a column for the current commit as part of
 486          * graph->num_parents.  If the current commit was already in
 487          * graph->columns, then we have double counted it.
 488          */
 489         if (is_commit_in_existing_columns)
 490                 max_cols--;
 491
 492         /*
 493          * Each column takes up 2 spaces
 494          */
 495         graph->width = max_cols * 2;
 496 }
 497
 498 static void graph_update_columns(struct git_graph *graph)
 499 {
 500         struct commit_list *parent;
 501         int max_new_columns;
 502         int mapping_idx;
 503         int i, seen_this, is_commit_in_columns;
 504
 505         /*
 506          * Swap graph->columns with graph->new_columns
 507          * graph->columns contains the state for the previous commit,
 508          * and new_columns now contains the state for our commit.
 509          *
 510          * We'll re-use the old columns array as storage to compute the new
 511          * columns list for the commit after this one.
 512          */
 513         SWAP(graph->columns, graph->new_columns);
 514         graph->num_columns = graph->num_new_columns;
 515         graph->num_new_columns = 0;
 516
 517         /*
 518          * Now update new_columns and mapping with the information for the
 519          * commit after this one.
 520          *
 521          * First, make sure we have enough room.  At most, there will
 522          * be graph->num_columns + graph->num_parents columns for the next
 523          * commit.
 524          */
 525         max_new_columns = graph->num_columns + graph->num_parents;
 526         graph_ensure_capacity(graph, max_new_columns);
 527
 528         /*
 529          * Clear out graph->mapping
 530          */
 531         graph->mapping_size = 2 * max_new_columns;
 532         for (i = 0; i < graph->mapping_size; i++)
 533                 graph->mapping[i] = -1;
 534
 535         /*
 536          * Populate graph->new_columns and graph->mapping
 537          *
 538          * Some of the parents of this commit may already be in
 539          * graph->columns.  If so, graph->new_columns should only contain a
 540          * single entry for each such commit.  graph->mapping should
 541          * contain information about where each current branch line is
 542          * supposed to end up after the collapsing is performed.
 543          */
 544         seen_this = 0;
 545         mapping_idx = 0;
 546         is_commit_in_columns = 1;
 547         for (i = 0; i <= graph->num_columns; i++) {
 548                 struct commit *col_commit;
 549                 if (i == graph->num_columns) {
 550                         if (seen_this)
 551                                 break;
 552                         is_commit_in_columns = 0;
 553                         col_commit = graph->commit;
 554                 } else {
 555                         col_commit = graph->columns[i].commit;
 556                 }
 557
 558                 if (col_commit == graph->commit) {
 559                         int old_mapping_idx = mapping_idx;
 560                         seen_this = 1;
 561                         graph->commit_index = i;
 562                         for (parent = first_interesting_parent(graph);
 563                              parent;
 564                              parent = next_interesting_parent(graph, parent)) {
 565                                 /*
 566                                  * If this is a merge, or the start of a new
 567                                  * childless column, increment the current
 568                                  * color.
 569                                  */
 570                                 if (graph->num_parents > 1 ||
 571                                     !is_commit_in_columns) {
 572                                         graph_increment_column_color(graph);
 573                                 }
 574                                 graph_insert_into_new_columns(graph,
 575                                                               parent->item,
 576                                                               &mapping_idx);
 577                         }
 578                         /*
 579                          * We always need to increment mapping_idx by at
 580                          * least 2, even if it has no interesting parents.
 581                          * The current commit always takes up at least 2
 582                          * spaces.
 583                          */
 584                         if (mapping_idx == old_mapping_idx)
 585                                 mapping_idx += 2;
 586                 } else {
 587                         graph_insert_into_new_columns(graph, col_commit,
 588                                                       &mapping_idx);
 589                 }
 590         }
 591
 592         /*
 593          * Shrink mapping_size to be the minimum necessary
 594          */
 595         while (graph->mapping_size > 1 &&
 596                graph->mapping[graph->mapping_size - 1] < 0)
 597                 graph->mapping_size--;
 598
 599         /*
 600          * Compute graph->width for this commit
 601          */
 602         graph_update_width(graph, is_commit_in_columns);
 603 }
 604
 605 void graph_update(struct git_graph *graph, struct commit *commit)
 606 {
 607         struct commit_list *parent;
 608
 609         /*
 610          * Set the new commit
 611          */
 612         graph->commit = commit;
 613
 614         /*
 615          * Count how many interesting parents this commit has
 616          */
 617         graph->num_parents = 0;
 618         for (parent = first_interesting_parent(graph);
 619              parent;
 620              parent = next_interesting_parent(graph, parent))
 621         {
 622                 graph->num_parents++;
 623         }
 624
 625         /*
 626          * Store the old commit_index in prev_commit_index.
 627          * graph_update_columns() will update graph->commit_index for this
 628          * commit.
 629          */
 630         graph->prev_commit_index = graph->commit_index;
 631
 632         /*
 633          * Call graph_update_columns() to update
 634          * columns, new_columns, and mapping.
 635          */
 636         graph_update_columns(graph);
 637
 638         graph->expansion_row = 0;
 639
 640         /*
 641          * Update graph->state.
 642          * Note that we don't call graph_update_state() here, since
 643          * we don't want to update graph->prev_state.  No line for
 644          * graph->state was ever printed.
 645          *
 646          * If the previous commit didn't get to the GRAPH_PADDING state,
 647          * it never finished its output.  Goto GRAPH_SKIP, to print out
 648          * a line to indicate that portion of the graph is missing.
 649          *
 650          * If there are 3 or more parents, we may need to print extra rows
 651          * before the commit, to expand the branch lines around it and make
 652          * room for it.  We need to do this only if there is a branch row
 653          * (or more) to the right of this commit.
 654          *
 655          * If there are less than 3 parents, we can immediately print the
 656          * commit line.
 657          */
 658         if (graph->state != GRAPH_PADDING)
 659                 graph->state = GRAPH_SKIP;
 660         else if (graph->num_parents >= 3 &&
 661                  graph->commit_index < (graph->num_columns - 1))
 662                 graph->state = GRAPH_PRE_COMMIT;
 663         else
 664                 graph->state = GRAPH_COMMIT;
 665 }
 666
 667 static int graph_is_mapping_correct(struct git_graph *graph)
 668 {
 669         int i;
 670
 671         /*
 672          * The mapping is up to date if each entry is at its target,
 673          * or is 1 greater than its target.
 674          * (If it is 1 greater than the target, '/' will be printed, so it
 675          * will look correct on the next row.)
 676          */
 677         for (i = 0; i < graph->mapping_size; i++) {
 678                 int target = graph->mapping[i];
 679                 if (target < 0)
 680                         continue;
 681                 if (target == (i / 2))
 682                         continue;
 683                 return 0;
 684         }
 685
 686         return 1;
 687 }
 688
 689 static void graph_pad_horizontally(struct git_graph *graph, struct strbuf *sb,
 690                                    int chars_written)
 691 {
 692         /*
 693          * Add additional spaces to the end of the strbuf, so that all
 694          * lines for a particular commit have the same width.
 695          *
 696          * This way, fields printed to the right of the graph will remain
 697          * aligned for the entire commit.
 698          */
 699         if (chars_written < graph->width)
 700                 strbuf_addchars(sb, ' ', graph->width - chars_written);
 701 }
 702
 703 static void graph_output_padding_line(struct git_graph *graph,
 704                                       struct strbuf *sb)
 705 {
 706         int i;
 707
 708         /*
 709          * We could conceivable be called with a NULL commit
 710          * if our caller has a bug, and invokes graph_next_line()
 711          * immediately after graph_init(), without first calling
 712          * graph_update().  Return without outputting anything in this
 713          * case.
 714          */
 715         if (!graph->commit)
 716                 return;
 717
 718         /*
 719          * Output a padding row, that leaves all branch lines unchanged
 720          */
 721         for (i = 0; i < graph->num_new_columns; i++) {
 722                 strbuf_write_column(sb, &graph->new_columns[i], '|');
 723                 strbuf_addch(sb, ' ');
 724         }
 725
 726         graph_pad_horizontally(graph, sb, graph->num_new_columns * 2);
 727 }
 728
 729
 730 int graph_width(struct git_graph *graph)
 731 {
 732         return graph->width;
 733 }
 734
 735
 736 static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
 737 {
 738         /*
 739          * Output an ellipsis to indicate that a portion
 740          * of the graph is missing.
 741          */
 742         strbuf_addstr(sb, "...");
 743         graph_pad_horizontally(graph, sb, 3);
 744
 745         if (graph->num_parents >= 3 &&
 746             graph->commit_index < (graph->num_columns - 1))
 747                 graph_update_state(graph, GRAPH_PRE_COMMIT);
 748         else
 749                 graph_update_state(graph, GRAPH_COMMIT);
 750 }
 751
 752 static void graph_output_pre_commit_line(struct git_graph *graph,
 753                                          struct strbuf *sb)
 754 {
 755         int num_expansion_rows;
 756         int i, seen_this;
 757         int chars_written;
 758
 759         /*
 760          * This function formats a row that increases the space around a commit
 761          * with multiple parents, to make room for it.  It should only be
 762          * called when there are 3 or more parents.
 763          *
 764          * We need 2 extra rows for every parent over 2.
 765          */
 766         assert(graph->num_parents >= 3);
 767         num_expansion_rows = (graph->num_parents - 2) * 2;
 768
 769         /*
 770          * graph->expansion_row tracks the current expansion row we are on.
 771          * It should be in the range [0, num_expansion_rows - 1]
 772          */
 773         assert(0 <= graph->expansion_row &&
 774                graph->expansion_row < num_expansion_rows);
 775
 776         /*
 777          * Output the row
 778          */
 779         seen_this = 0;
 780         chars_written = 0;
 781         for (i = 0; i < graph->num_columns; i++) {
 782                 struct column *col = &graph->columns[i];
 783                 if (col->commit == graph->commit) {
 784                         seen_this = 1;
 785                         strbuf_write_column(sb, col, '|');
 786                         strbuf_addchars(sb, ' ', graph->expansion_row);
 787                         chars_written += 1 + graph->expansion_row;
 788                 } else if (seen_this && (graph->expansion_row == 0)) {
 789                         /*
 790                          * This is the first line of the pre-commit output.
 791                          * If the previous commit was a merge commit and
 792                          * ended in the GRAPH_POST_MERGE state, all branch
 793                          * lines after graph->prev_commit_index were
 794                          * printed as "\" on the previous line.  Continue
 795                          * to print them as "\" on this line.  Otherwise,
 796                          * print the branch lines as "|".
 797                          */
 798                         if (graph->prev_state == GRAPH_POST_MERGE &&
 799                             graph->prev_commit_index < i)
 800                                 strbuf_write_column(sb, col, '\\');
 801                         else
 802                                 strbuf_write_column(sb, col, '|');
 803                         chars_written++;
 804                 } else if (seen_this && (graph->expansion_row > 0)) {
 805                         strbuf_write_column(sb, col, '\\');
 806                         chars_written++;
 807                 } else {
 808                         strbuf_write_column(sb, col, '|');
 809                         chars_written++;
 810                 }
 811                 strbuf_addch(sb, ' ');
 812                 chars_written++;
 813         }
 814
 815         graph_pad_horizontally(graph, sb, chars_written);
 816
 817         /*
 818          * Increment graph->expansion_row,
 819          * and move to state GRAPH_COMMIT if necessary
 820          */
 821         graph->expansion_row++;
 822         if (graph->expansion_row >= num_expansion_rows)
 823                 graph_update_state(graph, GRAPH_COMMIT);
 824 }
 825
 826 static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
 827 {
 828         /*
 829          * For boundary commits, print 'o'
 830          * (We should only see boundary commits when revs->boundary is set.)
 831          */
 832         if (graph->commit->object.flags & BOUNDARY) {
 833                 assert(graph->revs->boundary);
 834                 strbuf_addch(sb, 'o');
 835                 return;
 836         }
 837
 838         /*
 839          * get_revision_mark() handles all other cases without assert()
 840          */
 841         strbuf_addstr(sb, get_revision_mark(graph->revs, graph->commit));
 842 }
 843
 844 /*
 845  * Draw the horizontal dashes of an octopus merge and return the number of
 846  * characters written.
 847  */
 848 static int graph_draw_octopus_merge(struct git_graph *graph,
 849                                     struct strbuf *sb)
 850 {
 851         /*
 852          * Here dashless_parents represents the number of parents which don't
 853          * need to have dashes (the edges labeled "0" and "1").  And
 854          * dashful_parents are the remaining ones.
 855          *
 856          * | *---.
 857          * | |\ \ \
 858          * | | | | |
 859          * x 0 1 2 3
 860          *
 861          */
 862         const int dashless_parents = 2;
 863         int dashful_parents = graph->num_parents - dashless_parents;
 864
 865         /*
 866          * Usually, we add one new column for each parent (like the diagram
 867          * above) but sometimes the first parent goes into an existing column,
 868          * like this:
 869          *
 870          * | *---.
 871          * | |\ \ \
 872          * |/ / / /
 873          * x 0 1 2
 874          *
 875          * In which case the number of parents will be one greater than the
 876          * number of added columns.
 877          */
 878         int added_cols = (graph->num_new_columns - graph->num_columns);
 879         int parent_in_old_cols = graph->num_parents - added_cols;
 880
 881         /*
 882          * In both cases, commit_index corresponds to the edge labeled "0".
 883          */
 884         int first_col = graph->commit_index + dashless_parents
 885             - parent_in_old_cols;
 886
 887         int i;
 888         for (i = 0; i < dashful_parents; i++) {
 889                 strbuf_write_column(sb, &graph->new_columns[i+first_col], '-');
 890                 strbuf_write_column(sb, &graph->new_columns[i+first_col],
 891                                     i == dashful_parents-1 ? '.' : '-');
 892         }
 893         return 2 * dashful_parents;
 894 }
 895
 896 static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
 897 {
 898         int seen_this = 0;
 899         int i, chars_written;
 900
 901         /*
 902          * Output the row containing this commit
 903          * Iterate up to and including graph->num_columns,
 904          * since the current commit may not be in any of the existing
 905          * columns.  (This happens when the current commit doesn't have any
 906          * children that we have already processed.)
 907          */
 908         seen_this = 0;
 909         chars_written = 0;
 910         for (i = 0; i <= graph->num_columns; i++) {
 911                 struct column *col = &graph->columns[i];
 912                 struct commit *col_commit;
 913                 if (i == graph->num_columns) {
 914                         if (seen_this)
 915                                 break;
 916                         col_commit = graph->commit;
 917                 } else {
 918                         col_commit = graph->columns[i].commit;
 919                 }
 920
 921                 if (col_commit == graph->commit) {
 922                         seen_this = 1;
 923                         graph_output_commit_char(graph, sb);
 924                         chars_written++;
 925
 926                         if (graph->num_parents > 2)
 927                                 chars_written += graph_draw_octopus_merge(graph,
 928                                                                           sb);
 929                 } else if (seen_this && (graph->num_parents > 2)) {
 930                         strbuf_write_column(sb, col, '\\');
 931                         chars_written++;
 932                 } else if (seen_this && (graph->num_parents == 2)) {
 933                         /*
 934                          * This is a 2-way merge commit.
 935                          * There is no GRAPH_PRE_COMMIT stage for 2-way
 936                          * merges, so this is the first line of output
 937                          * for this commit.  Check to see what the previous
 938                          * line of output was.
 939                          *
 940                          * If it was GRAPH_POST_MERGE, the branch line
 941                          * coming into this commit may have been '\',
 942                          * and not '|' or '/'.  If so, output the branch
 943                          * line as '\' on this line, instead of '|'.  This
 944                          * makes the output look nicer.
 945                          */
 946                         if (graph->prev_state == GRAPH_POST_MERGE &&
 947                             graph->prev_commit_index < i)
 948                                 strbuf_write_column(sb, col, '\\');
 949                         else
 950                                 strbuf_write_column(sb, col, '|');
 951                         chars_written++;
 952                 } else {
 953                         strbuf_write_column(sb, col, '|');
 954                         chars_written++;
 955                 }
 956                 strbuf_addch(sb, ' ');
 957                 chars_written++;
 958         }
 959
 960         graph_pad_horizontally(graph, sb, chars_written);
 961
 962         /*
 963          * Update graph->state
 964          */
 965         if (graph->num_parents > 1)
 966                 graph_update_state(graph, GRAPH_POST_MERGE);
 967         else if (graph_is_mapping_correct(graph))
 968                 graph_update_state(graph, GRAPH_PADDING);
 969         else
 970                 graph_update_state(graph, GRAPH_COLLAPSING);
 971 }
 972
 973 static struct column *find_new_column_by_commit(struct git_graph *graph,
 974                                                 struct commit *commit)
 975 {
 976         int i;
 977         for (i = 0; i < graph->num_new_columns; i++) {
 978                 if (graph->new_columns[i].commit == commit)
 979                         return &graph->new_columns[i];
 980         }
 981         return NULL;
 982 }
 983
 984 static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
 985 {
 986         int seen_this = 0;
 987         int i, j, chars_written;
 988
 989         /*
 990          * Output the post-merge row
 991          */
 992         chars_written = 0;
 993         for (i = 0; i <= graph->num_columns; i++) {
 994                 struct column *col = &graph->columns[i];
 995                 struct commit *col_commit;
 996                 if (i == graph->num_columns) {
 997                         if (seen_this)
 998                                 break;
 999                         col_commit = graph->commit;
1000                 } else {
1001                         col_commit = col->commit;
1002                 }
1003
1004                 if (col_commit == graph->commit) {
1005                         /*
1006                          * Since the current commit is a merge find
1007                          * the columns for the parent commits in
1008                          * new_columns and use those to format the
1009                          * edges.
1010                          */
1011                         struct commit_list *parents = NULL;
1012                         struct column *par_column;
1013                         seen_this = 1;
1014                         parents = first_interesting_parent(graph);
1015                         assert(parents);
1016                         par_column = find_new_column_by_commit(graph, parents->item);
1017                         assert(par_column);
1018
1019                         strbuf_write_column(sb, par_column, '|');
1020                         chars_written++;
1021                         for (j = 0; j < graph->num_parents - 1; j++) {
1022                                 parents = next_interesting_parent(graph, parents);
1023                                 assert(parents);
1024                                 par_column = find_new_column_by_commit(graph, parents->item);
1025                                 assert(par_column);
1026                                 strbuf_write_column(sb, par_column, '\\');
1027                                 strbuf_addch(sb, ' ');
1028                         }
1029                         chars_written += j * 2;
1030                 } else if (seen_this) {
1031                         strbuf_write_column(sb, col, '\\');
1032                         strbuf_addch(sb, ' ');
1033                         chars_written += 2;
1034                 } else {
1035                         strbuf_write_column(sb, col, '|');
1036                         strbuf_addch(sb, ' ');
1037                         chars_written += 2;
1038                 }
1039         }
1040
1041         graph_pad_horizontally(graph, sb, chars_written);
1042
1043         /*
1044          * Update graph->state
1045          */
1046         if (graph_is_mapping_correct(graph))
1047                 graph_update_state(graph, GRAPH_PADDING);
1048         else
1049                 graph_update_state(graph, GRAPH_COLLAPSING);
1050 }
1051
1052 static void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
1053 {
1054         int i;
1055         short used_horizontal = 0;
1056         int horizontal_edge = -1;
1057         int horizontal_edge_target = -1;
1058
1059         /*
1060          * Clear out the new_mapping array
1061          */
1062         for (i = 0; i < graph->mapping_size; i++)
1063                 graph->new_mapping[i] = -1;
1064
1065         for (i = 0; i < graph->mapping_size; i++) {
1066                 int target = graph->mapping[i];
1067                 if (target < 0)
1068                         continue;
1069
1070                 /*
1071                  * Since update_columns() always inserts the leftmost
1072                  * column first, each branch's target location should
1073                  * always be either its current location or to the left of
1074                  * its current location.
1075                  *
1076                  * We never have to move branches to the right.  This makes
1077                  * the graph much more legible, since whenever branches
1078                  * cross, only one is moving directions.
1079                  */
1080                 assert(target * 2 <= i);
1081
1082                 if (target * 2 == i) {
1083                         /*
1084                          * This column is already in the
1085                          * correct place
1086                          */
1087                         assert(graph->new_mapping[i] == -1);
1088                         graph->new_mapping[i] = target;
1089                 } else if (graph->new_mapping[i - 1] < 0) {
1090                         /*
1091                          * Nothing is to the left.
1092                          * Move to the left by one
1093                          */
1094                         graph->new_mapping[i - 1] = target;
1095                         /*
1096                          * If there isn't already an edge moving horizontally
1097                          * select this one.
1098                          */
1099                         if (horizontal_edge == -1) {
1100                                 int j;
1101                                 horizontal_edge = i;
1102                                 horizontal_edge_target = target;
1103                                 /*
1104                                  * The variable target is the index of the graph
1105                                  * column, and therefore target*2+3 is the
1106                                  * actual screen column of the first horizontal
1107                                  * line.
1108                                  */
1109                                 for (j = (target * 2)+3; j < (i - 2); j += 2)
1110                                         graph->new_mapping[j] = target;
1111                         }
1112                 } else if (graph->new_mapping[i - 1] == target) {
1113                         /*
1114                          * There is a branch line to our left
1115                          * already, and it is our target.  We
1116                          * combine with this line, since we share
1117                          * the same parent commit.
1118                          *
1119                          * We don't have to add anything to the
1120                          * output or new_mapping, since the
1121                          * existing branch line has already taken
1122                          * care of it.
1123                          */
1124                 } else {
1125                         /*
1126                          * There is a branch line to our left,
1127                          * but it isn't our target.  We need to
1128                          * cross over it.
1129                          *
1130                          * The space just to the left of this
1131                          * branch should always be empty.
1132                          *
1133                          * The branch to the left of that space
1134                          * should be our eventual target.
1135                          */
1136                         assert(graph->new_mapping[i - 1] > target);
1137                         assert(graph->new_mapping[i - 2] < 0);
1138                         assert(graph->new_mapping[i - 3] == target);
1139                         graph->new_mapping[i - 2] = target;
1140                         /*
1141                          * Mark this branch as the horizontal edge to
1142                          * prevent any other edges from moving
1143                          * horizontally.
1144                          */
1145                         if (horizontal_edge == -1)
1146                                 horizontal_edge = i;
1147                 }
1148         }
1149
1150         /*
1151          * The new mapping may be 1 smaller than the old mapping
1152          */
1153         if (graph->new_mapping[graph->mapping_size - 1] < 0)
1154                 graph->mapping_size--;
1155
1156         /*
1157          * Output out a line based on the new mapping info
1158          */
1159         for (i = 0; i < graph->mapping_size; i++) {
1160                 int target = graph->new_mapping[i];
1161                 if (target < 0)
1162                         strbuf_addch(sb, ' ');
1163                 else if (target * 2 == i)
1164                         strbuf_write_column(sb, &graph->new_columns[target], '|');
1165                 else if (target == horizontal_edge_target &&
1166                          i != horizontal_edge - 1) {
1167                                 /*
1168                                  * Set the mappings for all but the
1169                                  * first segment to -1 so that they
1170                                  * won't continue into the next line.
1171                                  */
1172                                 if (i != (target * 2)+3)
1173                                         graph->new_mapping[i] = -1;
1174                                 used_horizontal = 1;
1175                         strbuf_write_column(sb, &graph->new_columns[target], '_');
1176                 } else {
1177                         if (used_horizontal && i < horizontal_edge)
1178                                 graph->new_mapping[i] = -1;
1179                         strbuf_write_column(sb, &graph->new_columns[target], '/');
1180
1181                 }
1182         }
1183
1184         graph_pad_horizontally(graph, sb, graph->mapping_size);
1185
1186         /*
1187          * Swap mapping and new_mapping
1188          */
1189         SWAP(graph->mapping, graph->new_mapping);
1190
1191         /*
1192          * If graph->mapping indicates that all of the branch lines
1193          * are already in the correct positions, we are done.
1194          * Otherwise, we need to collapse some branch lines together.
1195          */
1196         if (graph_is_mapping_correct(graph))
1197                 graph_update_state(graph, GRAPH_PADDING);
1198 }
1199
1200 int graph_next_line(struct git_graph *graph, struct strbuf *sb)
1201 {
1202         switch (graph->state) {
1203         case GRAPH_PADDING:
1204                 graph_output_padding_line(graph, sb);
1205                 return 0;
1206         case GRAPH_SKIP:
1207                 graph_output_skip_line(graph, sb);
1208                 return 0;
1209         case GRAPH_PRE_COMMIT:
1210                 graph_output_pre_commit_line(graph, sb);
1211                 return 0;
1212         case GRAPH_COMMIT:
1213                 graph_output_commit_line(graph, sb);
1214                 return 1;
1215         case GRAPH_POST_MERGE:
1216                 graph_output_post_merge_line(graph, sb);
1217                 return 0;
1218         case GRAPH_COLLAPSING:
1219                 graph_output_collapsing_line(graph, sb);
1220                 return 0;
1221         }
1222
1223         assert(0);
1224         return 0;
1225 }
1226
1227 static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
1228 {
1229         int i;
1230         int chars_written = 0;
1231
1232         if (graph->state != GRAPH_COMMIT) {
1233                 graph_next_line(graph, sb);
1234                 return;
1235         }
1236
1237         /*
1238          * Output the row containing this commit
1239          * Iterate up to and including graph->num_columns,
1240          * since the current commit may not be in any of the existing
1241          * columns.  (This happens when the current commit doesn't have any
1242          * children that we have already processed.)
1243          */
1244         for (i = 0; i < graph->num_columns; i++) {
1245                 struct column *col = &graph->columns[i];
1246
1247                 strbuf_write_column(sb, col, '|');
1248                 chars_written++;
1249
1250                 if (col->commit == graph->commit && graph->num_parents > 2) {
1251                         int len = (graph->num_parents - 2) * 2;
1252                         strbuf_addchars(sb, ' ', len);
1253                         chars_written += len;
1254                 } else {
1255                         strbuf_addch(sb, ' ');
1256                         chars_written++;
1257                 }
1258         }
1259
1260         graph_pad_horizontally(graph, sb, chars_written);
1261
1262         /*
1263          * Update graph->prev_state since we have output a padding line
1264          */
1265         graph->prev_state = GRAPH_PADDING;
1266 }
1267
1268 int graph_is_commit_finished(struct git_graph const *graph)
1269 {
1270         return (graph->state == GRAPH_PADDING);
1271 }
1272
1273 void graph_show_commit(struct git_graph *graph)
1274 {
1275         struct strbuf msgbuf = STRBUF_INIT;
1276         int shown_commit_line = 0;
1277
1278         graph_show_line_prefix(default_diffopt);
1279
1280         if (!graph)
1281                 return;
1282
1283         /*
1284          * When showing a diff of a merge against each of its parents, we
1285          * are called once for each parent without graph_update having been
1286          * called.  In this case, simply output a single padding line.
1287          */
1288         if (graph_is_commit_finished(graph)) {
1289                 graph_show_padding(graph);
1290                 shown_commit_line = 1;
1291         }
1292
1293         while (!shown_commit_line && !graph_is_commit_finished(graph)) {
1294                 shown_commit_line = graph_next_line(graph, &msgbuf);
1295                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1296                         graph->revs->diffopt.file);
1297                 if (!shown_commit_line) {
1298                         putc('\n', graph->revs->diffopt.file);
1299                         graph_show_line_prefix(&graph->revs->diffopt);
1300                 }
1301                 strbuf_setlen(&msgbuf, 0);
1302         }
1303
1304         strbuf_release(&msgbuf);
1305 }
1306
1307 void graph_show_oneline(struct git_graph *graph)
1308 {
1309         struct strbuf msgbuf = STRBUF_INIT;
1310
1311         graph_show_line_prefix(default_diffopt);
1312
1313         if (!graph)
1314                 return;
1315
1316         graph_next_line(graph, &msgbuf);
1317         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1318         strbuf_release(&msgbuf);
1319 }
1320
1321 void graph_show_padding(struct git_graph *graph)
1322 {
1323         struct strbuf msgbuf = STRBUF_INIT;
1324
1325         graph_show_line_prefix(default_diffopt);
1326
1327         if (!graph)
1328                 return;
1329
1330         graph_padding_line(graph, &msgbuf);
1331         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1332         strbuf_release(&msgbuf);
1333 }
1334
1335 int graph_show_remainder(struct git_graph *graph)
1336 {
1337         struct strbuf msgbuf = STRBUF_INIT;
1338         int shown = 0;
1339
1340         graph_show_line_prefix(default_diffopt);
1341
1342         if (!graph)
1343                 return 0;
1344
1345         if (graph_is_commit_finished(graph))
1346                 return 0;
1347
1348         for (;;) {
1349                 graph_next_line(graph, &msgbuf);
1350                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1351                         graph->revs->diffopt.file);
1352                 strbuf_setlen(&msgbuf, 0);
1353                 shown = 1;
1354
1355                 if (!graph_is_commit_finished(graph)) {
1356                         putc('\n', graph->revs->diffopt.file);
1357                         graph_show_line_prefix(&graph->revs->diffopt);
1358                 } else {
1359                         break;
1360                 }
1361         }
1362         strbuf_release(&msgbuf);
1363
1364         return shown;
1365 }
1366
1367 static void graph_show_strbuf(struct git_graph *graph,
1368                               FILE *file,
1369                               struct strbuf const *sb)
1370 {
1371         char *p;
1372
1373         /*
1374          * Print the strbuf line by line,
1375          * and display the graph info before each line but the first.
1376          */
1377         p = sb->buf;
1378         while (p) {
1379                 size_t len;
1380                 char *next_p = strchr(p, '\n');
1381                 if (next_p) {
1382                         next_p++;
1383                         len = next_p - p;
1384                 } else {
1385                         len = (sb->buf + sb->len) - p;
1386                 }
1387                 fwrite(p, sizeof(char), len, file);
1388                 if (next_p && *next_p != '\0')
1389                         graph_show_oneline(graph);
1390                 p = next_p;
1391         }
1392 }
1393
1394 void graph_show_commit_msg(struct git_graph *graph,
1395                            FILE *file,
1396                            struct strbuf const *sb)
1397 {
1398         int newline_terminated;
1399
1400         /*
1401          * Show the commit message
1402          */
1403         graph_show_strbuf(graph, file, sb);
1404
1405         if (!graph)
1406                 return;
1407
1408         newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1409
1410         /*
1411          * If there is more output needed for this commit, show it now
1412          */
1413         if (!graph_is_commit_finished(graph)) {
1414                 /*
1415                  * If sb doesn't have a terminating newline, print one now,
1416                  * so we can start the remainder of the graph output on a
1417                  * new line.
1418                  */
1419                 if (!newline_terminated)
1420                         putc('\n', file);
1421
1422                 graph_show_remainder(graph);
1423
1424                 /*
1425                  * If sb ends with a newline, our output should too.
1426                  */
1427                 if (newline_terminated)
1428                         putc('\n', file);
1429         }
1430 }