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