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