graph.con commit Merge branch 'jc/utf8-fprintf' (62458ea)
   1#include "cache.h"
   2#include "config.h"
   3#include "commit.h"
   4#include "color.h"
   5#include "graph.h"
   6#include "revision.h"
   7#include "argv-array.h"
   8
   9/* Internal API */
  10
  11/*
  12 * Output a padding line in the graph.
  13 * This is similar to graph_next_line().  However, it is guaranteed to
  14 * never print the current commit line.  Instead, if the commit line is
  15 * next, it will simply output a line of vertical padding, extending the
  16 * branch lines downwards, but leaving them otherwise unchanged.
  17 */
  18static void graph_padding_line(struct git_graph *graph, struct strbuf *sb);
  19
  20/*
  21 * Print a strbuf.  If the graph is non-NULL, all lines but the first will be
  22 * prefixed with the graph output.
  23 *
  24 * If the strbuf ends with a newline, the output will end after this
  25 * newline.  A new graph line will not be printed after the final newline.
  26 * If the strbuf is empty, no output will be printed.
  27 *
  28 * Since the first line will not include the graph output, the caller is
  29 * responsible for printing this line's graph (perhaps via
  30 * graph_show_commit() or graph_show_oneline()) before calling
  31 * graph_show_strbuf().
  32 *
  33 * Note that unlike some other graph display functions, you must pass the file
  34 * handle directly. It is assumed that this is the same file handle as the
  35 * file specified by the graph diff options. This is necessary so that
  36 * graph_show_strbuf can be called even with a NULL graph.
  37 */
  38static void graph_show_strbuf(struct git_graph *graph,
  39                              FILE *file,
  40                              struct strbuf const *sb);
  41
  42/*
  43 * TODO:
  44 * - Limit the number of columns, similar to the way gitk does.
  45 *   If we reach more than a specified number of columns, omit
  46 *   sections of some columns.
  47 */
  48
  49struct column {
  50        /*
  51         * The parent commit of this column.
  52         */
  53        struct commit *commit;
  54        /*
  55         * The color to (optionally) print this column in.  This is an
  56         * index into column_colors.
  57         */
  58        unsigned short color;
  59};
  60
  61enum graph_state {
  62        GRAPH_PADDING,
  63        GRAPH_SKIP,
  64        GRAPH_PRE_COMMIT,
  65        GRAPH_COMMIT,
  66        GRAPH_POST_MERGE,
  67        GRAPH_COLLAPSING
  68};
  69
  70static void graph_show_line_prefix(const struct diff_options *diffopt)
  71{
  72        if (!diffopt || !diffopt->line_prefix)
  73                return;
  74
  75        fwrite(diffopt->line_prefix,
  76               sizeof(char),
  77               diffopt->line_prefix_length,
  78               diffopt->file);
  79}
  80
  81static const char **column_colors;
  82static unsigned short column_colors_max;
  83
  84static void parse_graph_colors_config(struct argv_array *colors, const char *string)
  85{
  86        const char *end, *start;
  87
  88        start = string;
  89        end = string + strlen(string);
  90        while (start < end) {
  91                const char *comma = strchrnul(start, ',');
  92                char color[COLOR_MAXLEN];
  93
  94                if (!color_parse_mem(start, comma - start, color))
  95                        argv_array_push(colors, color);
  96                else
  97                        warning(_("ignore invalid color '%.*s' in log.graphColors"),
  98                                (int)(comma - start), start);
  99                start = comma + 1;
 100        }
 101        argv_array_push(colors, GIT_COLOR_RESET);
 102}
 103
 104void graph_set_column_colors(const char **colors, unsigned short colors_max)
 105{
 106        column_colors = colors;
 107        column_colors_max = colors_max;
 108}
 109
 110static const char *column_get_color_code(unsigned short color)
 111{
 112        return column_colors[color];
 113}
 114
 115static void strbuf_write_column(struct strbuf *sb, const struct column *c,
 116                                char col_char)
 117{
 118        if (c->color < column_colors_max)
 119                strbuf_addstr(sb, column_get_color_code(c->color));
 120        strbuf_addch(sb, col_char);
 121        if (c->color < column_colors_max)
 122                strbuf_addstr(sb, column_get_color_code(column_colors_max));
 123}
 124
 125struct git_graph {
 126        /*
 127         * The commit currently being processed
 128         */
 129        struct commit *commit;
 130        /* The rev-info used for the current traversal */
 131        struct rev_info *revs;
 132        /*
 133         * The number of interesting parents that this commit has.
 134         *
 135         * Note that this is not the same as the actual number of parents.
 136         * This count excludes parents that won't be printed in the graph
 137         * output, as determined by graph_is_interesting().
 138         */
 139        int num_parents;
 140        /*
 141         * The width of the graph output for this commit.
 142         * All rows for this commit are padded to this width, so that
 143         * messages printed after the graph output are aligned.
 144         */
 145        int width;
 146        /*
 147         * The next expansion row to print
 148         * when state is GRAPH_PRE_COMMIT
 149         */
 150        int expansion_row;
 151        /*
 152         * The current output state.
 153         * This tells us what kind of line graph_next_line() should output.
 154         */
 155        enum graph_state state;
 156        /*
 157         * The output state for the previous line of output.
 158         * This is primarily used to determine how the first merge line
 159         * should appear, based on the last line of the previous commit.
 160         */
 161        enum graph_state prev_state;
 162        /*
 163         * The index of the column that refers to this commit.
 164         *
 165         * If none of the incoming columns refer to this commit,
 166         * this will be equal to num_columns.
 167         */
 168        int commit_index;
 169        /*
 170         * The commit_index for the previously displayed commit.
 171         *
 172         * This is used to determine how the first line of a merge
 173         * graph output should appear, based on the last line of the
 174         * previous commit.
 175         */
 176        int prev_commit_index;
 177        /*
 178         * The maximum number of columns that can be stored in the columns
 179         * and new_columns arrays.  This is also half the number of entries
 180         * that can be stored in the mapping and new_mapping arrays.
 181         */
 182        int column_capacity;
 183        /*
 184         * The number of columns (also called "branch lines" in some places)
 185         */
 186        int num_columns;
 187        /*
 188         * The number of columns in the new_columns array
 189         */
 190        int num_new_columns;
 191        /*
 192         * The number of entries in the mapping array
 193         */
 194        int mapping_size;
 195        /*
 196         * The column state before we output the current commit.
 197         */
 198        struct column *columns;
 199        /*
 200         * The new column state after we output the current commit.
 201         * Only valid when state is GRAPH_COLLAPSING.
 202         */
 203        struct column *new_columns;
 204        /*
 205         * An array that tracks the current state of each
 206         * character in the output line during state GRAPH_COLLAPSING.
 207         * Each entry is -1 if this character is empty, or a non-negative
 208         * integer if the character contains a branch line.  The value of
 209         * the integer indicates the target position for this branch line.
 210         * (I.e., this array maps the current column positions to their
 211         * desired positions.)
 212         *
 213         * The maximum capacity of this array is always
 214         * sizeof(int) * 2 * column_capacity.
 215         */
 216        int *mapping;
 217        /*
 218         * A temporary array for computing the next mapping state
 219         * while we are outputting a mapping line.  This is stored as part
 220         * of the git_graph simply so we don't have to allocate a new
 221         * temporary array each time we have to output a collapsing line.
 222         */
 223        int *new_mapping;
 224        /*
 225         * The current default column color being used.  This is
 226         * stored as an index into the array column_colors.
 227         */
 228        unsigned short default_column_color;
 229};
 230
 231static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void *data)
 232{
 233        struct git_graph *graph = data;
 234        static struct strbuf msgbuf = STRBUF_INIT;
 235
 236        assert(opt);
 237
 238        strbuf_reset(&msgbuf);
 239        if (opt->line_prefix)
 240                strbuf_add(&msgbuf, opt->line_prefix,
 241                           opt->line_prefix_length);
 242        if (graph)
 243                graph_padding_line(graph, &msgbuf);
 244        return &msgbuf;
 245}
 246
 247static const struct diff_options *default_diffopt;
 248
 249void graph_setup_line_prefix(struct diff_options *diffopt)
 250{
 251        default_diffopt = diffopt;
 252
 253        /* setup an output prefix callback if necessary */
 254        if (diffopt && !diffopt->output_prefix)
 255                diffopt->output_prefix = diff_output_prefix_callback;
 256}
 257
 258
 259struct git_graph *graph_init(struct rev_info *opt)
 260{
 261        struct git_graph *graph = xmalloc(sizeof(struct git_graph));
 262
 263        if (!column_colors) {
 264                char *string;
 265                if (git_config_get_string("log.graphcolors", &string)) {
 266                        /* not configured -- use default */
 267                        graph_set_column_colors(column_colors_ansi,
 268                                                column_colors_ansi_max);
 269                } else {
 270                        static struct argv_array custom_colors = ARGV_ARRAY_INIT;
 271                        argv_array_clear(&custom_colors);
 272                        parse_graph_colors_config(&custom_colors, string);
 273                        free(string);
 274                        /* graph_set_column_colors takes a max-index, not a count */
 275                        graph_set_column_colors(custom_colors.argv,
 276                                                custom_colors.argc - 1);
 277                }
 278        }
 279
 280        graph->commit = NULL;
 281        graph->revs = opt;
 282        graph->num_parents = 0;
 283        graph->expansion_row = 0;
 284        graph->state = GRAPH_PADDING;
 285        graph->prev_state = GRAPH_PADDING;
 286        graph->commit_index = 0;
 287        graph->prev_commit_index = 0;
 288        graph->num_columns = 0;
 289        graph->num_new_columns = 0;
 290        graph->mapping_size = 0;
 291        /*
 292         * Start the column color at the maximum value, since we'll
 293         * always increment it for the first commit we output.
 294         * This way we start at 0 for the first commit.
 295         */
 296        graph->default_column_color = column_colors_max - 1;
 297
 298        /*
 299         * Allocate a reasonably large default number of columns
 300         * We'll automatically grow columns later if we need more room.
 301         */
 302        graph->column_capacity = 30;
 303        ALLOC_ARRAY(graph->columns, graph->column_capacity);
 304        ALLOC_ARRAY(graph->new_columns, graph->column_capacity);
 305        ALLOC_ARRAY(graph->mapping, 2 * graph->column_capacity);
 306        ALLOC_ARRAY(graph->new_mapping, 2 * graph->column_capacity);
 307
 308        /*
 309         * The diff output prefix callback, with this we can make
 310         * all the diff output to align with the graph lines.
 311         */
 312        opt->diffopt.output_prefix = diff_output_prefix_callback;
 313        opt->diffopt.output_prefix_data = graph;
 314
 315        return graph;
 316}
 317
 318static void graph_update_state(struct git_graph *graph, enum graph_state s)
 319{
 320        graph->prev_state = graph->state;
 321        graph->state = s;
 322}
 323
 324static void graph_ensure_capacity(struct git_graph *graph, int num_columns)
 325{
 326        if (graph->column_capacity >= num_columns)
 327                return;
 328
 329        do {
 330                graph->column_capacity *= 2;
 331        } while (graph->column_capacity < num_columns);
 332
 333        REALLOC_ARRAY(graph->columns, graph->column_capacity);
 334        REALLOC_ARRAY(graph->new_columns, graph->column_capacity);
 335        REALLOC_ARRAY(graph->mapping, graph->column_capacity * 2);
 336        REALLOC_ARRAY(graph->new_mapping, graph->column_capacity * 2);
 337}
 338
 339/*
 340 * Returns 1 if the commit will be printed in the graph output,
 341 * and 0 otherwise.
 342 */
 343static int graph_is_interesting(struct git_graph *graph, struct commit *commit)
 344{
 345        /*
 346         * If revs->boundary is set, commits whose children have
 347         * been shown are always interesting, even if they have the
 348         * UNINTERESTING or TREESAME flags set.
 349         */
 350        if (graph->revs && graph->revs->boundary) {
 351                if (commit->object.flags & CHILD_SHOWN)
 352                        return 1;
 353        }
 354
 355        /*
 356         * Otherwise, use get_commit_action() to see if this commit is
 357         * interesting
 358         */
 359        return get_commit_action(graph->revs, commit) == commit_show;
 360}
 361
 362static struct commit_list *next_interesting_parent(struct git_graph *graph,
 363                                                   struct commit_list *orig)
 364{
 365        struct commit_list *list;
 366
 367        /*
 368         * If revs->first_parent_only is set, only the first
 369         * parent is interesting.  None of the others are.
 370         */
 371        if (graph->revs->first_parent_only)
 372                return NULL;
 373
 374        /*
 375         * Return the next interesting commit after orig
 376         */
 377        for (list = orig->next; list; list = list->next) {
 378                if (graph_is_interesting(graph, list->item))
 379                        return list;
 380        }
 381
 382        return NULL;
 383}
 384
 385static struct commit_list *first_interesting_parent(struct git_graph *graph)
 386{
 387        struct commit_list *parents = graph->commit->parents;
 388
 389        /*
 390         * If this commit has no parents, ignore it
 391         */
 392        if (!parents)
 393                return NULL;
 394
 395        /*
 396         * If the first parent is interesting, return it
 397         */
 398        if (graph_is_interesting(graph, parents->item))
 399                return parents;
 400
 401        /*
 402         * Otherwise, call next_interesting_parent() to get
 403         * the next interesting parent
 404         */
 405        return next_interesting_parent(graph, parents);
 406}
 407
 408static unsigned short graph_get_current_column_color(const struct git_graph *graph)
 409{
 410        if (!want_color(graph->revs->diffopt.use_color))
 411                return column_colors_max;
 412        return graph->default_column_color;
 413}
 414
 415/*
 416 * Update the graph's default column color.
 417 */
 418static void graph_increment_column_color(struct git_graph *graph)
 419{
 420        graph->default_column_color = (graph->default_column_color + 1) %
 421                column_colors_max;
 422}
 423
 424static unsigned short graph_find_commit_color(const struct git_graph *graph,
 425                                              const struct commit *commit)
 426{
 427        int i;
 428        for (i = 0; i < graph->num_columns; i++) {
 429                if (graph->columns[i].commit == commit)
 430                        return graph->columns[i].color;
 431        }
 432        return graph_get_current_column_color(graph);
 433}
 434
 435static void graph_insert_into_new_columns(struct git_graph *graph,
 436                                          struct commit *commit,
 437                                          int *mapping_index)
 438{
 439        int i;
 440
 441        /*
 442         * If the commit is already in the new_columns list, we don't need to
 443         * add it.  Just update the mapping correctly.
 444         */
 445        for (i = 0; i < graph->num_new_columns; i++) {
 446                if (graph->new_columns[i].commit == commit) {
 447                        graph->mapping[*mapping_index] = i;
 448                        *mapping_index += 2;
 449                        return;
 450                }
 451        }
 452
 453        /*
 454         * This commit isn't already in new_columns.  Add it.
 455         */
 456        graph->new_columns[graph->num_new_columns].commit = commit;
 457        graph->new_columns[graph->num_new_columns].color = graph_find_commit_color(graph, commit);
 458        graph->mapping[*mapping_index] = graph->num_new_columns;
 459        *mapping_index += 2;
 460        graph->num_new_columns++;
 461}
 462
 463static void graph_update_width(struct git_graph *graph,
 464                               int is_commit_in_existing_columns)
 465{
 466        /*
 467         * Compute the width needed to display the graph for this commit.
 468         * This is the maximum width needed for any row.  All other rows
 469         * will be padded to this width.
 470         *
 471         * Compute the number of columns in the widest row:
 472         * Count each existing column (graph->num_columns), and each new
 473         * column added by this commit.
 474         */
 475        int max_cols = graph->num_columns + graph->num_parents;
 476
 477        /*
 478         * Even if the current commit has no parents to be printed, it
 479         * still takes up a column for itself.
 480         */
 481        if (graph->num_parents < 1)
 482                max_cols++;
 483
 484        /*
 485         * We added a column for the current commit as part of
 486         * graph->num_parents.  If the current commit was already in
 487         * graph->columns, then we have double counted it.
 488         */
 489        if (is_commit_in_existing_columns)
 490                max_cols--;
 491
 492        /*
 493         * Each column takes up 2 spaces
 494         */
 495        graph->width = max_cols * 2;
 496}
 497
 498static void graph_update_columns(struct git_graph *graph)
 499{
 500        struct commit_list *parent;
 501        int max_new_columns;
 502        int mapping_idx;
 503        int i, seen_this, is_commit_in_columns;
 504
 505        /*
 506         * Swap graph->columns with graph->new_columns
 507         * graph->columns contains the state for the previous commit,
 508         * and new_columns now contains the state for our commit.
 509         *
 510         * We'll re-use the old columns array as storage to compute the new
 511         * columns list for the commit after this one.
 512         */
 513        SWAP(graph->columns, graph->new_columns);
 514        graph->num_columns = graph->num_new_columns;
 515        graph->num_new_columns = 0;
 516
 517        /*
 518         * Now update new_columns and mapping with the information for the
 519         * commit after this one.
 520         *
 521         * First, make sure we have enough room.  At most, there will
 522         * be graph->num_columns + graph->num_parents columns for the next
 523         * commit.
 524         */
 525        max_new_columns = graph->num_columns + graph->num_parents;
 526        graph_ensure_capacity(graph, max_new_columns);
 527
 528        /*
 529         * Clear out graph->mapping
 530         */
 531        graph->mapping_size = 2 * max_new_columns;
 532        for (i = 0; i < graph->mapping_size; i++)
 533                graph->mapping[i] = -1;
 534
 535        /*
 536         * Populate graph->new_columns and graph->mapping
 537         *
 538         * Some of the parents of this commit may already be in
 539         * graph->columns.  If so, graph->new_columns should only contain a
 540         * single entry for each such commit.  graph->mapping should
 541         * contain information about where each current branch line is
 542         * supposed to end up after the collapsing is performed.
 543         */
 544        seen_this = 0;
 545        mapping_idx = 0;
 546        is_commit_in_columns = 1;
 547        for (i = 0; i <= graph->num_columns; i++) {
 548                struct commit *col_commit;
 549                if (i == graph->num_columns) {
 550                        if (seen_this)
 551                                break;
 552                        is_commit_in_columns = 0;
 553                        col_commit = graph->commit;
 554                } else {
 555                        col_commit = graph->columns[i].commit;
 556                }
 557
 558                if (col_commit == graph->commit) {
 559                        int old_mapping_idx = mapping_idx;
 560                        seen_this = 1;
 561                        graph->commit_index = i;
 562                        for (parent = first_interesting_parent(graph);
 563                             parent;
 564                             parent = next_interesting_parent(graph, parent)) {
 565                                /*
 566                                 * If this is a merge, or the start of a new
 567                                 * childless column, increment the current
 568                                 * color.
 569                                 */
 570                                if (graph->num_parents > 1 ||
 571                                    !is_commit_in_columns) {
 572                                        graph_increment_column_color(graph);
 573                                }
 574                                graph_insert_into_new_columns(graph,
 575                                                              parent->item,
 576                                                              &mapping_idx);
 577                        }
 578                        /*
 579                         * We always need to increment mapping_idx by at
 580                         * least 2, even if it has no interesting parents.
 581                         * The current commit always takes up at least 2
 582                         * spaces.
 583                         */
 584                        if (mapping_idx == old_mapping_idx)
 585                                mapping_idx += 2;
 586                } else {
 587                        graph_insert_into_new_columns(graph, col_commit,
 588                                                      &mapping_idx);
 589                }
 590        }
 591
 592        /*
 593         * Shrink mapping_size to be the minimum necessary
 594         */
 595        while (graph->mapping_size > 1 &&
 596               graph->mapping[graph->mapping_size - 1] < 0)
 597                graph->mapping_size--;
 598
 599        /*
 600         * Compute graph->width for this commit
 601         */
 602        graph_update_width(graph, is_commit_in_columns);
 603}
 604
 605void graph_update(struct git_graph *graph, struct commit *commit)
 606{
 607        struct commit_list *parent;
 608
 609        /*
 610         * Set the new commit
 611         */
 612        graph->commit = commit;
 613
 614        /*
 615         * Count how many interesting parents this commit has
 616         */
 617        graph->num_parents = 0;
 618        for (parent = first_interesting_parent(graph);
 619             parent;
 620             parent = next_interesting_parent(graph, parent))
 621        {
 622                graph->num_parents++;
 623        }
 624
 625        /*
 626         * Store the old commit_index in prev_commit_index.
 627         * graph_update_columns() will update graph->commit_index for this
 628         * commit.
 629         */
 630        graph->prev_commit_index = graph->commit_index;
 631
 632        /*
 633         * Call graph_update_columns() to update
 634         * columns, new_columns, and mapping.
 635         */
 636        graph_update_columns(graph);
 637
 638        graph->expansion_row = 0;
 639
 640        /*
 641         * Update graph->state.
 642         * Note that we don't call graph_update_state() here, since
 643         * we don't want to update graph->prev_state.  No line for
 644         * graph->state was ever printed.
 645         *
 646         * If the previous commit didn't get to the GRAPH_PADDING state,
 647         * it never finished its output.  Goto GRAPH_SKIP, to print out
 648         * a line to indicate that portion of the graph is missing.
 649         *
 650         * If there are 3 or more parents, we may need to print extra rows
 651         * before the commit, to expand the branch lines around it and make
 652         * room for it.  We need to do this only if there is a branch row
 653         * (or more) to the right of this commit.
 654         *
 655         * If there are less than 3 parents, we can immediately print the
 656         * commit line.
 657         */
 658        if (graph->state != GRAPH_PADDING)
 659                graph->state = GRAPH_SKIP;
 660        else if (graph->num_parents >= 3 &&
 661                 graph->commit_index < (graph->num_columns - 1))
 662                graph->state = GRAPH_PRE_COMMIT;
 663        else
 664                graph->state = GRAPH_COMMIT;
 665}
 666
 667static int graph_is_mapping_correct(struct git_graph *graph)
 668{
 669        int i;
 670
 671        /*
 672         * The mapping is up to date if each entry is at its target,
 673         * or is 1 greater than its target.
 674         * (If it is 1 greater than the target, '/' will be printed, so it
 675         * will look correct on the next row.)
 676         */
 677        for (i = 0; i < graph->mapping_size; i++) {
 678                int target = graph->mapping[i];
 679                if (target < 0)
 680                        continue;
 681                if (target == (i / 2))
 682                        continue;
 683                return 0;
 684        }
 685
 686        return 1;
 687}
 688
 689static void graph_pad_horizontally(struct git_graph *graph, struct strbuf *sb,
 690                                   int chars_written)
 691{
 692        /*
 693         * Add additional spaces to the end of the strbuf, so that all
 694         * lines for a particular commit have the same width.
 695         *
 696         * This way, fields printed to the right of the graph will remain
 697         * aligned for the entire commit.
 698         */
 699        int extra;
 700        if (chars_written >= graph->width)
 701                return;
 702
 703        extra = graph->width - chars_written;
 704        strbuf_addf(sb, "%*s", (int) extra, "");
 705}
 706
 707static void graph_output_padding_line(struct git_graph *graph,
 708                                      struct strbuf *sb)
 709{
 710        int i;
 711
 712        /*
 713         * We could conceivable be called with a NULL commit
 714         * if our caller has a bug, and invokes graph_next_line()
 715         * immediately after graph_init(), without first calling
 716         * graph_update().  Return without outputting anything in this
 717         * case.
 718         */
 719        if (!graph->commit)
 720                return;
 721
 722        /*
 723         * Output a padding row, that leaves all branch lines unchanged
 724         */
 725        for (i = 0; i < graph->num_new_columns; i++) {
 726                strbuf_write_column(sb, &graph->new_columns[i], '|');
 727                strbuf_addch(sb, ' ');
 728        }
 729
 730        graph_pad_horizontally(graph, sb, graph->num_new_columns * 2);
 731}
 732
 733
 734int graph_width(struct git_graph *graph)
 735{
 736        return graph->width;
 737}
 738
 739
 740static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
 741{
 742        /*
 743         * Output an ellipsis to indicate that a portion
 744         * of the graph is missing.
 745         */
 746        strbuf_addstr(sb, "...");
 747        graph_pad_horizontally(graph, sb, 3);
 748
 749        if (graph->num_parents >= 3 &&
 750            graph->commit_index < (graph->num_columns - 1))
 751                graph_update_state(graph, GRAPH_PRE_COMMIT);
 752        else
 753                graph_update_state(graph, GRAPH_COMMIT);
 754}
 755
 756static void graph_output_pre_commit_line(struct git_graph *graph,
 757                                         struct strbuf *sb)
 758{
 759        int num_expansion_rows;
 760        int i, seen_this;
 761        int chars_written;
 762
 763        /*
 764         * This function formats a row that increases the space around a commit
 765         * with multiple parents, to make room for it.  It should only be
 766         * called when there are 3 or more parents.
 767         *
 768         * We need 2 extra rows for every parent over 2.
 769         */
 770        assert(graph->num_parents >= 3);
 771        num_expansion_rows = (graph->num_parents - 2) * 2;
 772
 773        /*
 774         * graph->expansion_row tracks the current expansion row we are on.
 775         * It should be in the range [0, num_expansion_rows - 1]
 776         */
 777        assert(0 <= graph->expansion_row &&
 778               graph->expansion_row < num_expansion_rows);
 779
 780        /*
 781         * Output the row
 782         */
 783        seen_this = 0;
 784        chars_written = 0;
 785        for (i = 0; i < graph->num_columns; i++) {
 786                struct column *col = &graph->columns[i];
 787                if (col->commit == graph->commit) {
 788                        seen_this = 1;
 789                        strbuf_write_column(sb, col, '|');
 790                        strbuf_addf(sb, "%*s", graph->expansion_row, "");
 791                        chars_written += 1 + graph->expansion_row;
 792                } else if (seen_this && (graph->expansion_row == 0)) {
 793                        /*
 794                         * This is the first line of the pre-commit output.
 795                         * If the previous commit was a merge commit and
 796                         * ended in the GRAPH_POST_MERGE state, all branch
 797                         * lines after graph->prev_commit_index were
 798                         * printed as "\" on the previous line.  Continue
 799                         * to print them as "\" on this line.  Otherwise,
 800                         * print the branch lines as "|".
 801                         */
 802                        if (graph->prev_state == GRAPH_POST_MERGE &&
 803                            graph->prev_commit_index < i)
 804                                strbuf_write_column(sb, col, '\\');
 805                        else
 806                                strbuf_write_column(sb, col, '|');
 807                        chars_written++;
 808                } else if (seen_this && (graph->expansion_row > 0)) {
 809                        strbuf_write_column(sb, col, '\\');
 810                        chars_written++;
 811                } else {
 812                        strbuf_write_column(sb, col, '|');
 813                        chars_written++;
 814                }
 815                strbuf_addch(sb, ' ');
 816                chars_written++;
 817        }
 818
 819        graph_pad_horizontally(graph, sb, chars_written);
 820
 821        /*
 822         * Increment graph->expansion_row,
 823         * and move to state GRAPH_COMMIT if necessary
 824         */
 825        graph->expansion_row++;
 826        if (graph->expansion_row >= num_expansion_rows)
 827                graph_update_state(graph, GRAPH_COMMIT);
 828}
 829
 830static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
 831{
 832        /*
 833         * For boundary commits, print 'o'
 834         * (We should only see boundary commits when revs->boundary is set.)
 835         */
 836        if (graph->commit->object.flags & BOUNDARY) {
 837                assert(graph->revs->boundary);
 838                strbuf_addch(sb, 'o');
 839                return;
 840        }
 841
 842        /*
 843         * get_revision_mark() handles all other cases without assert()
 844         */
 845        strbuf_addstr(sb, get_revision_mark(graph->revs, graph->commit));
 846}
 847
 848/*
 849 * Draw an octopus merge and return the number of characters written.
 850 */
 851static int graph_draw_octopus_merge(struct git_graph *graph,
 852                                    struct strbuf *sb)
 853{
 854        /*
 855         * Here dashless_commits represents the number of parents
 856         * which don't need to have dashes (because their edges fit
 857         * neatly under the commit).
 858         */
 859        const int dashless_commits = 2;
 860        int col_num, i;
 861        int num_dashes =
 862                ((graph->num_parents - dashless_commits) * 2) - 1;
 863        for (i = 0; i < num_dashes; i++) {
 864                col_num = (i / 2) + dashless_commits + graph->commit_index;
 865                strbuf_write_column(sb, &graph->new_columns[col_num], '-');
 866        }
 867        col_num = (i / 2) + dashless_commits + graph->commit_index;
 868        strbuf_write_column(sb, &graph->new_columns[col_num], '.');
 869        return num_dashes + 1;
 870}
 871
 872static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
 873{
 874        int seen_this = 0;
 875        int i, chars_written;
 876
 877        /*
 878         * Output the row containing this commit
 879         * Iterate up to and including graph->num_columns,
 880         * since the current commit may not be in any of the existing
 881         * columns.  (This happens when the current commit doesn't have any
 882         * children that we have already processed.)
 883         */
 884        seen_this = 0;
 885        chars_written = 0;
 886        for (i = 0; i <= graph->num_columns; i++) {
 887                struct column *col = &graph->columns[i];
 888                struct commit *col_commit;
 889                if (i == graph->num_columns) {
 890                        if (seen_this)
 891                                break;
 892                        col_commit = graph->commit;
 893                } else {
 894                        col_commit = graph->columns[i].commit;
 895                }
 896
 897                if (col_commit == graph->commit) {
 898                        seen_this = 1;
 899                        graph_output_commit_char(graph, sb);
 900                        chars_written++;
 901
 902                        if (graph->num_parents > 2)
 903                                chars_written += graph_draw_octopus_merge(graph,
 904                                                                          sb);
 905                } else if (seen_this && (graph->num_parents > 2)) {
 906                        strbuf_write_column(sb, col, '\\');
 907                        chars_written++;
 908                } else if (seen_this && (graph->num_parents == 2)) {
 909                        /*
 910                         * This is a 2-way merge commit.
 911                         * There is no GRAPH_PRE_COMMIT stage for 2-way
 912                         * merges, so this is the first line of output
 913                         * for this commit.  Check to see what the previous
 914                         * line of output was.
 915                         *
 916                         * If it was GRAPH_POST_MERGE, the branch line
 917                         * coming into this commit may have been '\',
 918                         * and not '|' or '/'.  If so, output the branch
 919                         * line as '\' on this line, instead of '|'.  This
 920                         * makes the output look nicer.
 921                         */
 922                        if (graph->prev_state == GRAPH_POST_MERGE &&
 923                            graph->prev_commit_index < i)
 924                                strbuf_write_column(sb, col, '\\');
 925                        else
 926                                strbuf_write_column(sb, col, '|');
 927                        chars_written++;
 928                } else {
 929                        strbuf_write_column(sb, col, '|');
 930                        chars_written++;
 931                }
 932                strbuf_addch(sb, ' ');
 933                chars_written++;
 934        }
 935
 936        graph_pad_horizontally(graph, sb, chars_written);
 937
 938        /*
 939         * Update graph->state
 940         */
 941        if (graph->num_parents > 1)
 942                graph_update_state(graph, GRAPH_POST_MERGE);
 943        else if (graph_is_mapping_correct(graph))
 944                graph_update_state(graph, GRAPH_PADDING);
 945        else
 946                graph_update_state(graph, GRAPH_COLLAPSING);
 947}
 948
 949static struct column *find_new_column_by_commit(struct git_graph *graph,
 950                                                struct commit *commit)
 951{
 952        int i;
 953        for (i = 0; i < graph->num_new_columns; i++) {
 954                if (graph->new_columns[i].commit == commit)
 955                        return &graph->new_columns[i];
 956        }
 957        return NULL;
 958}
 959
 960static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
 961{
 962        int seen_this = 0;
 963        int i, j, chars_written;
 964
 965        /*
 966         * Output the post-merge row
 967         */
 968        chars_written = 0;
 969        for (i = 0; i <= graph->num_columns; i++) {
 970                struct column *col = &graph->columns[i];
 971                struct commit *col_commit;
 972                if (i == graph->num_columns) {
 973                        if (seen_this)
 974                                break;
 975                        col_commit = graph->commit;
 976                } else {
 977                        col_commit = col->commit;
 978                }
 979
 980                if (col_commit == graph->commit) {
 981                        /*
 982                         * Since the current commit is a merge find
 983                         * the columns for the parent commits in
 984                         * new_columns and use those to format the
 985                         * edges.
 986                         */
 987                        struct commit_list *parents = NULL;
 988                        struct column *par_column;
 989                        seen_this = 1;
 990                        parents = first_interesting_parent(graph);
 991                        assert(parents);
 992                        par_column = find_new_column_by_commit(graph, parents->item);
 993                        assert(par_column);
 994
 995                        strbuf_write_column(sb, par_column, '|');
 996                        chars_written++;
 997                        for (j = 0; j < graph->num_parents - 1; j++) {
 998                                parents = next_interesting_parent(graph, parents);
 999                                assert(parents);
1000                                par_column = find_new_column_by_commit(graph, parents->item);
1001                                assert(par_column);
1002                                strbuf_write_column(sb, par_column, '\\');
1003                                strbuf_addch(sb, ' ');
1004                        }
1005                        chars_written += j * 2;
1006                } else if (seen_this) {
1007                        strbuf_write_column(sb, col, '\\');
1008                        strbuf_addch(sb, ' ');
1009                        chars_written += 2;
1010                } else {
1011                        strbuf_write_column(sb, col, '|');
1012                        strbuf_addch(sb, ' ');
1013                        chars_written += 2;
1014                }
1015        }
1016
1017        graph_pad_horizontally(graph, sb, chars_written);
1018
1019        /*
1020         * Update graph->state
1021         */
1022        if (graph_is_mapping_correct(graph))
1023                graph_update_state(graph, GRAPH_PADDING);
1024        else
1025                graph_update_state(graph, GRAPH_COLLAPSING);
1026}
1027
1028static void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
1029{
1030        int i;
1031        short used_horizontal = 0;
1032        int horizontal_edge = -1;
1033        int horizontal_edge_target = -1;
1034
1035        /*
1036         * Clear out the new_mapping array
1037         */
1038        for (i = 0; i < graph->mapping_size; i++)
1039                graph->new_mapping[i] = -1;
1040
1041        for (i = 0; i < graph->mapping_size; i++) {
1042                int target = graph->mapping[i];
1043                if (target < 0)
1044                        continue;
1045
1046                /*
1047                 * Since update_columns() always inserts the leftmost
1048                 * column first, each branch's target location should
1049                 * always be either its current location or to the left of
1050                 * its current location.
1051                 *
1052                 * We never have to move branches to the right.  This makes
1053                 * the graph much more legible, since whenever branches
1054                 * cross, only one is moving directions.
1055                 */
1056                assert(target * 2 <= i);
1057
1058                if (target * 2 == i) {
1059                        /*
1060                         * This column is already in the
1061                         * correct place
1062                         */
1063                        assert(graph->new_mapping[i] == -1);
1064                        graph->new_mapping[i] = target;
1065                } else if (graph->new_mapping[i - 1] < 0) {
1066                        /*
1067                         * Nothing is to the left.
1068                         * Move to the left by one
1069                         */
1070                        graph->new_mapping[i - 1] = target;
1071                        /*
1072                         * If there isn't already an edge moving horizontally
1073                         * select this one.
1074                         */
1075                        if (horizontal_edge == -1) {
1076                                int j;
1077                                horizontal_edge = i;
1078                                horizontal_edge_target = target;
1079                                /*
1080                                 * The variable target is the index of the graph
1081                                 * column, and therefore target*2+3 is the
1082                                 * actual screen column of the first horizontal
1083                                 * line.
1084                                 */
1085                                for (j = (target * 2)+3; j < (i - 2); j += 2)
1086                                        graph->new_mapping[j] = target;
1087                        }
1088                } else if (graph->new_mapping[i - 1] == target) {
1089                        /*
1090                         * There is a branch line to our left
1091                         * already, and it is our target.  We
1092                         * combine with this line, since we share
1093                         * the same parent commit.
1094                         *
1095                         * We don't have to add anything to the
1096                         * output or new_mapping, since the
1097                         * existing branch line has already taken
1098                         * care of it.
1099                         */
1100                } else {
1101                        /*
1102                         * There is a branch line to our left,
1103                         * but it isn't our target.  We need to
1104                         * cross over it.
1105                         *
1106                         * The space just to the left of this
1107                         * branch should always be empty.
1108                         *
1109                         * The branch to the left of that space
1110                         * should be our eventual target.
1111                         */
1112                        assert(graph->new_mapping[i - 1] > target);
1113                        assert(graph->new_mapping[i - 2] < 0);
1114                        assert(graph->new_mapping[i - 3] == target);
1115                        graph->new_mapping[i - 2] = target;
1116                        /*
1117                         * Mark this branch as the horizontal edge to
1118                         * prevent any other edges from moving
1119                         * horizontally.
1120                         */
1121                        if (horizontal_edge == -1)
1122                                horizontal_edge = i;
1123                }
1124        }
1125
1126        /*
1127         * The new mapping may be 1 smaller than the old mapping
1128         */
1129        if (graph->new_mapping[graph->mapping_size - 1] < 0)
1130                graph->mapping_size--;
1131
1132        /*
1133         * Output out a line based on the new mapping info
1134         */
1135        for (i = 0; i < graph->mapping_size; i++) {
1136                int target = graph->new_mapping[i];
1137                if (target < 0)
1138                        strbuf_addch(sb, ' ');
1139                else if (target * 2 == i)
1140                        strbuf_write_column(sb, &graph->new_columns[target], '|');
1141                else if (target == horizontal_edge_target &&
1142                         i != horizontal_edge - 1) {
1143                                /*
1144                                 * Set the mappings for all but the
1145                                 * first segment to -1 so that they
1146                                 * won't continue into the next line.
1147                                 */
1148                                if (i != (target * 2)+3)
1149                                        graph->new_mapping[i] = -1;
1150                                used_horizontal = 1;
1151                        strbuf_write_column(sb, &graph->new_columns[target], '_');
1152                } else {
1153                        if (used_horizontal && i < horizontal_edge)
1154                                graph->new_mapping[i] = -1;
1155                        strbuf_write_column(sb, &graph->new_columns[target], '/');
1156
1157                }
1158        }
1159
1160        graph_pad_horizontally(graph, sb, graph->mapping_size);
1161
1162        /*
1163         * Swap mapping and new_mapping
1164         */
1165        SWAP(graph->mapping, graph->new_mapping);
1166
1167        /*
1168         * If graph->mapping indicates that all of the branch lines
1169         * are already in the correct positions, we are done.
1170         * Otherwise, we need to collapse some branch lines together.
1171         */
1172        if (graph_is_mapping_correct(graph))
1173                graph_update_state(graph, GRAPH_PADDING);
1174}
1175
1176int graph_next_line(struct git_graph *graph, struct strbuf *sb)
1177{
1178        switch (graph->state) {
1179        case GRAPH_PADDING:
1180                graph_output_padding_line(graph, sb);
1181                return 0;
1182        case GRAPH_SKIP:
1183                graph_output_skip_line(graph, sb);
1184                return 0;
1185        case GRAPH_PRE_COMMIT:
1186                graph_output_pre_commit_line(graph, sb);
1187                return 0;
1188        case GRAPH_COMMIT:
1189                graph_output_commit_line(graph, sb);
1190                return 1;
1191        case GRAPH_POST_MERGE:
1192                graph_output_post_merge_line(graph, sb);
1193                return 0;
1194        case GRAPH_COLLAPSING:
1195                graph_output_collapsing_line(graph, sb);
1196                return 0;
1197        }
1198
1199        assert(0);
1200        return 0;
1201}
1202
1203static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
1204{
1205        int i;
1206        int chars_written = 0;
1207
1208        if (graph->state != GRAPH_COMMIT) {
1209                graph_next_line(graph, sb);
1210                return;
1211        }
1212
1213        /*
1214         * Output the row containing this commit
1215         * Iterate up to and including graph->num_columns,
1216         * since the current commit may not be in any of the existing
1217         * columns.  (This happens when the current commit doesn't have any
1218         * children that we have already processed.)
1219         */
1220        for (i = 0; i < graph->num_columns; i++) {
1221                struct column *col = &graph->columns[i];
1222
1223                strbuf_write_column(sb, col, '|');
1224                chars_written++;
1225
1226                if (col->commit == graph->commit && graph->num_parents > 2) {
1227                        int len = (graph->num_parents - 2) * 2;
1228                        strbuf_addchars(sb, ' ', len);
1229                        chars_written += len;
1230                } else {
1231                        strbuf_addch(sb, ' ');
1232                        chars_written++;
1233                }
1234        }
1235
1236        graph_pad_horizontally(graph, sb, chars_written);
1237
1238        /*
1239         * Update graph->prev_state since we have output a padding line
1240         */
1241        graph->prev_state = GRAPH_PADDING;
1242}
1243
1244int graph_is_commit_finished(struct git_graph const *graph)
1245{
1246        return (graph->state == GRAPH_PADDING);
1247}
1248
1249void graph_show_commit(struct git_graph *graph)
1250{
1251        struct strbuf msgbuf = STRBUF_INIT;
1252        int shown_commit_line = 0;
1253
1254        graph_show_line_prefix(default_diffopt);
1255
1256        if (!graph)
1257                return;
1258
1259        /*
1260         * When showing a diff of a merge against each of its parents, we
1261         * are called once for each parent without graph_update having been
1262         * called.  In this case, simply output a single padding line.
1263         */
1264        if (graph_is_commit_finished(graph)) {
1265                graph_show_padding(graph);
1266                shown_commit_line = 1;
1267        }
1268
1269        while (!shown_commit_line && !graph_is_commit_finished(graph)) {
1270                shown_commit_line = graph_next_line(graph, &msgbuf);
1271                fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1272                        graph->revs->diffopt.file);
1273                if (!shown_commit_line) {
1274                        putc('\n', graph->revs->diffopt.file);
1275                        graph_show_line_prefix(&graph->revs->diffopt);
1276                }
1277                strbuf_setlen(&msgbuf, 0);
1278        }
1279
1280        strbuf_release(&msgbuf);
1281}
1282
1283void graph_show_oneline(struct git_graph *graph)
1284{
1285        struct strbuf msgbuf = STRBUF_INIT;
1286
1287        graph_show_line_prefix(default_diffopt);
1288
1289        if (!graph)
1290                return;
1291
1292        graph_next_line(graph, &msgbuf);
1293        fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1294        strbuf_release(&msgbuf);
1295}
1296
1297void graph_show_padding(struct git_graph *graph)
1298{
1299        struct strbuf msgbuf = STRBUF_INIT;
1300
1301        graph_show_line_prefix(default_diffopt);
1302
1303        if (!graph)
1304                return;
1305
1306        graph_padding_line(graph, &msgbuf);
1307        fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1308        strbuf_release(&msgbuf);
1309}
1310
1311int graph_show_remainder(struct git_graph *graph)
1312{
1313        struct strbuf msgbuf = STRBUF_INIT;
1314        int shown = 0;
1315
1316        graph_show_line_prefix(default_diffopt);
1317
1318        if (!graph)
1319                return 0;
1320
1321        if (graph_is_commit_finished(graph))
1322                return 0;
1323
1324        for (;;) {
1325                graph_next_line(graph, &msgbuf);
1326                fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1327                        graph->revs->diffopt.file);
1328                strbuf_setlen(&msgbuf, 0);
1329                shown = 1;
1330
1331                if (!graph_is_commit_finished(graph)) {
1332                        putc('\n', graph->revs->diffopt.file);
1333                        graph_show_line_prefix(&graph->revs->diffopt);
1334                } else {
1335                        break;
1336                }
1337        }
1338        strbuf_release(&msgbuf);
1339
1340        return shown;
1341}
1342
1343static void graph_show_strbuf(struct git_graph *graph,
1344                              FILE *file,
1345                              struct strbuf const *sb)
1346{
1347        char *p;
1348
1349        /*
1350         * Print the strbuf line by line,
1351         * and display the graph info before each line but the first.
1352         */
1353        p = sb->buf;
1354        while (p) {
1355                size_t len;
1356                char *next_p = strchr(p, '\n');
1357                if (next_p) {
1358                        next_p++;
1359                        len = next_p - p;
1360                } else {
1361                        len = (sb->buf + sb->len) - p;
1362                }
1363                fwrite(p, sizeof(char), len, file);
1364                if (next_p && *next_p != '\0')
1365                        graph_show_oneline(graph);
1366                p = next_p;
1367        }
1368}
1369
1370void graph_show_commit_msg(struct git_graph *graph,
1371                           FILE *file,
1372                           struct strbuf const *sb)
1373{
1374        int newline_terminated;
1375
1376        /*
1377         * Show the commit message
1378         */
1379        graph_show_strbuf(graph, file, sb);
1380
1381        if (!graph)
1382                return;
1383
1384        newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1385
1386        /*
1387         * If there is more output needed for this commit, show it now
1388         */
1389        if (!graph_is_commit_finished(graph)) {
1390                /*
1391                 * If sb doesn't have a terminating newline, print one now,
1392                 * so we can start the remainder of the graph output on a
1393                 * new line.
1394                 */
1395                if (!newline_terminated)
1396                        putc('\n', file);
1397
1398                graph_show_remainder(graph);
1399
1400                /*
1401                 * If sb ends with a newline, our output should too.
1402                 */
1403                if (newline_terminated)
1404                        putc('\n', file);
1405        }
1406}