graph.c

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