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_release()` destroys a `struct git_graph`, and frees the memory 15 associated with it. 16 17* `graph_update()` moves the graph to a new commit. 18 19* `graph_next_line()` outputs the next line of the graph into a strbuf. It 20 does not add a terminating newline. 21 22* `graph_padding_line()` outputs a line of vertical padding in the graph. It 23 is similar to `graph_next_line()`, but is guaranteed to never print the line 24 containing the current commit. Where `graph_next_line()` would print the 25 commit line next, `graph_padding_line()` prints a line that simply extends 26 all branch lines downwards one row, leaving their positions unchanged. 27 28* `graph_is_commit_finished()` determines if the graph has output all lines 29 necessary for the current commit. If `graph_update()` is called before all 30 lines for the current commit have been printed, the next call to 31 `graph_next_line()` will output an ellipsis, to indicate that a portion of 32 the graph was omitted. 33 34The following utility functions are wrappers around `graph_next_line()` and 35`graph_is_commit_finished()`. They always print the output to stdout. 36They can all be called with a NULL graph argument, in which case no graph 37output will be printed. 38 39* `graph_show_commit()` calls `graph_next_line()` until it returns non-zero. 40 This prints all graph lines up to, and including, the line containing this 41 commit. Output is printed to stdout. The last line printed does not contain 42 a terminating newline. This should not be called if the commit line has 43 already been printed, or it will loop forever. 44 45* `graph_show_oneline()` calls `graph_next_line()` and prints the result to 46 stdout. The line printed does not contain a terminating newline. 47 48* `graph_show_padding()` calls `graph_padding_line()` and prints the result to 49 stdout. The line printed does not contain a terminating newline. 50 51* `graph_show_remainder()` calls `graph_next_line()` until 52 `graph_is_commit_finished()` returns non-zero. Output is printed to stdout. 53 The last line printed does not contain a terminating newline. Returns 1 if 54 output was printed, and 0 if no output was necessary. 55 56* `graph_show_strbuf()` prints the specified strbuf to stdout, prefixing all 57 lines but the first with a graph line. The caller is responsible for 58 ensuring graph output for the first line has already been printed to stdout. 59 (This can be done with `graph_show_commit()` or `graph_show_oneline()`.) If 60 a NULL graph is supplied, the strbuf is printed as-is. 61 62* `graph_show_commit_msg()` is similar to `graph_show_strbuf()`, but it also 63 prints the remainder of the graph, if more lines are needed after the strbuf 64 ends. It is better than directly calling `graph_show_strbuf()` followed by 65 `graph_show_remainder()` since it properly handles buffers that do not end in 66 a terminating newline. The output printed by `graph_show_commit_msg()` will 67 end in a newline if and only if the strbuf ends in a newline. 68 69Data structure 70-------------- 71`struct git_graph` is an opaque data type used to store the current graph 72state. 73 74Calling sequence 75---------------- 76 77* Create a `struct git_graph` by calling `graph_init()`. When using the 78 revision walking API, this is done automatically by `setup_revisions()` if 79 the '--graph' option is supplied. 80 81* Use the revision walking API to walk through a group of contiguous commits. 82 The `get_revision()` function automatically calls `graph_update()` each time 83 it is invoked. 84 85* For each commit, call `graph_next_line()` repeatedly, until 86 `graph_is_commit_finished()` returns non-zero. Each call go 87 `graph_next_line()` will output a single line of the graph. The resulting 88 lines will not contain any newlines. `graph_next_line()` returns 1 if the 89 resulting line contains the current commit, or 0 if this is merely a line 90 needed to adjust the graph before or after the current commit. This return 91 value can be used to determine where to print the commit summary information 92 alongside the graph output. 93 94Limitations 95----------- 96 97* `graph_update()` must be called with commits in topological order. It should 98 not be called on a commit if it has already been invoked with an ancestor of 99 that commit, or the graph output will be incorrect. 100 101* `graph_update()` must be called on a contiguous group of commits. If 102 `graph_update()` is called on a particular commit, it should later be called 103 on all parents of that commit. Parents must not be skipped, or the graph 104 output will appear incorrect. 105+ 106`graph_update()` may be used on a pruned set of commits only if the parent list 107has been rewritten so as to include only ancestors from the pruned set. 108 109* The graph API does not currently support reverse commit ordering. In 110 order to implement reverse ordering, the graphing API needs an 111 (efficient) mechanism to find the children of a commit. 112 113Sample usage 114------------ 115 116------------ 117struct commit *commit; 118struct git_graph *graph = graph_init(opts); 119 120while ((commit = get_revision(opts)) != NULL) { 121 graph_update(graph, commit); 122 while (!graph_is_commit_finished(graph)) 123 { 124 struct strbuf sb; 125 int is_commit_line; 126 127 strbuf_init(&sb, 0); 128 is_commit_line = graph_next_line(graph, &sb); 129 fputs(sb.buf, stdout); 130 131 if (is_commit_line) 132 log_tree_commit(opts, commit); 133 else 134 putchar(opts->diffopt.line_termination); 135 } 136} 137 138graph_release(graph); 139------------ 140 141Sample output 142------------- 143 144The following is an example of the output from the graph API. This output does 145not include any commit summary information--callers are responsible for 146outputting that information, if desired. 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|/ / / / / / 175* | | | | | 176| | | | | * 177| | | | |/ 178| | | | * 179------------