1history graph API 2================= 3 4The graph API is used to draw a text-based representation of the commit 5history. The API generates the graph in a line-by-line fashion. 6 7Functions 8--------- 9 10Core functions: 11 12* `graph_init()` creates a new `struct git_graph` 13 14* `graph_update()` moves the graph to a new commit. 15 16* `graph_next_line()` outputs the next line of the graph into a strbuf. It 17 does not add a terminating newline. 18 19* `graph_padding_line()` outputs a line of vertical padding in the graph. It 20 is similar to `graph_next_line()`, but is guaranteed to never print the line 21 containing the current commit. Where `graph_next_line()` would print the 22 commit line next, `graph_padding_line()` prints a line that simply extends 23 all branch lines downwards one row, leaving their positions unchanged. 24 25* `graph_is_commit_finished()` determines if the graph has output all lines 26 necessary for the current commit. If `graph_update()` is called before all 27 lines for the current commit have been printed, the next call to 28 `graph_next_line()` will output an ellipsis, to indicate that a portion of 29 the graph was omitted. 30 31The following utility functions are wrappers around `graph_next_line()` and 32`graph_is_commit_finished()`. They always print the output to stdout. 33They can all be called with a NULL graph argument, in which case no graph 34output will be printed. 35 36* `graph_show_commit()` calls `graph_next_line()` until it returns non-zero. 37 This prints all graph lines up to, and including, the line containing this 38 commit. Output is printed to stdout. The last line printed does not contain 39 a terminating newline. This should not be called if the commit line has 40 already been printed, or it will loop forever. 41 42* `graph_show_oneline()` calls `graph_next_line()` and prints the result to 43 stdout. The line printed does not contain a terminating newline. 44 45* `graph_show_padding()` calls `graph_padding_line()` and prints the result to 46 stdout. The line printed does not contain a terminating newline. 47 48* `graph_show_remainder()` calls `graph_next_line()` until 49 `graph_is_commit_finished()` returns non-zero. Output is printed to stdout. 50 The last line printed does not contain a terminating newline. Returns 1 if 51 output was printed, and 0 if no output was necessary. 52 53* `graph_show_strbuf()` prints the specified strbuf to stdout, prefixing all 54 lines but the first with a graph line. The caller is responsible for 55 ensuring graph output for the first line has already been printed to stdout. 56 (This can be done with `graph_show_commit()` or `graph_show_oneline()`.) If 57 a NULL graph is supplied, the strbuf is printed as-is. 58 59* `graph_show_commit_msg()` is similar to `graph_show_strbuf()`, but it also 60 prints the remainder of the graph, if more lines are needed after the strbuf 61 ends. It is better than directly calling `graph_show_strbuf()` followed by 62 `graph_show_remainder()` since it properly handles buffers that do not end in 63 a terminating newline. The output printed by `graph_show_commit_msg()` will 64 end in a newline if and only if the strbuf ends in a newline. 65 66Data structure 67-------------- 68`struct git_graph` is an opaque data type used to store the current graph 69state. 70 71Calling sequence 72---------------- 73 74* Create a `struct git_graph` by calling `graph_init()`. When using the 75 revision walking API, this is done automatically by `setup_revisions()` if 76 the '--graph' option is supplied. 77 78* Use the revision walking API to walk through a group of contiguous commits. 79 The `get_revision()` function automatically calls `graph_update()` each time 80 it is invoked. 81 82* For each commit, call `graph_next_line()` repeatedly, until 83 `graph_is_commit_finished()` returns non-zero. Each call go 84 `graph_next_line()` will output a single line of the graph. The resulting 85 lines will not contain any newlines. `graph_next_line()` returns 1 if the 86 resulting line contains the current commit, or 0 if this is merely a line 87 needed to adjust the graph before or after the current commit. This return 88 value can be used to determine where to print the commit summary information 89 alongside the graph output. 90 91Limitations 92----------- 93 94* `graph_update()` must be called with commits in topological order. It should 95 not be called on a commit if it has already been invoked with an ancestor of 96 that commit, or the graph output will be incorrect. 97 98* `graph_update()` must be called on a contiguous group of commits. If 99 `graph_update()` is called on a particular commit, it should later be called 100 on all parents of that commit. Parents must not be skipped, or the graph 101 output will appear incorrect. 102+ 103`graph_update()` may be used on a pruned set of commits only if the parent list 104has been rewritten so as to include only ancestors from the pruned set. 105 106* The graph API does not currently support reverse commit ordering. In 107 order to implement reverse ordering, the graphing API needs an 108 (efficient) mechanism to find the children of a commit. 109 110Sample usage 111------------ 112 113------------ 114struct commit *commit; 115struct git_graph *graph = graph_init(opts); 116 117while ((commit = get_revision(opts)) != NULL) { 118 graph_update(graph, commit); 119 while (!graph_is_commit_finished(graph)) 120 { 121 struct strbuf sb; 122 int is_commit_line; 123 124 strbuf_init(&sb, 0); 125 is_commit_line = graph_next_line(graph, &sb); 126 fputs(sb.buf, stdout); 127 128 if (is_commit_line) 129 log_tree_commit(opts, commit); 130 else 131 putchar(opts->diffopt.line_termination); 132 } 133} 134------------ 135 136Sample output 137------------- 138 139The following is an example of the output from the graph API. This output does 140not include any commit summary information--callers are responsible for 141outputting that information, if desired. 142 143------------ 144* 145* 146* 147|\ 148* | 149| | * 150| \ \ 151| \ \ 152*-. \ \ 153|\ \ \ \ 154| | * | | 155| | | | | * 156| | | | | * 157| | | | | * 158| | | | | |\ 159| | | | | | * 160| * | | | | | 161| | | | | * \ 162| | | | | |\ | 163| | | | * | | | 164| | | | * | | | 165* | | | | | | | 166| |/ / / / / / 167|/| / / / / / 168* | | | | | | 169|/ / / / / / 170* | | | | | 171| | | | | * 172| | | | |/ 173| | | | * 174------------