graph.c

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