graph.con commit Update draft release notes for 1.6.3.2 (40bad52)
   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 */
  19static 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 */
  28static 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 output, 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 */
  43static 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
  66struct 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
  78enum 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 */
  90static 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
 107static const char *column_get_color_code(const struct column *c)
 108{
 109        return column_colors[c->color];
 110}
 111
 112static 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
 122struct 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
 228struct 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
 259static 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
 265static 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 */
 290static 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
 308static 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
 331static 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
 354static 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 */
 364static 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
 370static 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
 381static 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
 409static 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
 444static 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
 552void 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
 614static 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
 636static 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
 654static 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
 680static 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
 696static 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 += 1 + 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
 770static 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 */
 804static 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
 825static 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 > 2)
 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
 902static 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
 913static 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
 981static 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
1086static 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
1113static 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
1156int graph_is_commit_finished(struct git_graph const *graph)
1157{
1158        return (graph->state == GRAPH_PADDING);
1159}
1160
1161void 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
1180void 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
1192void 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
1204int 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
1232static 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
1262void 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}