Calling sequence
----------------
-* Create a `struct git_graph` by calling `graph_init()`.
+* Create a `struct git_graph` by calling `graph_init()`. When using the
+ revision walking API, this is done automatically by `setup_revisions()` if
+ the '--graph' option is supplied.
* Use the revision walking API to walk through a group of contiguous commits.
+ The `get_revision()` function automatically calls `graph_update()` each time
+ it is invoked.
-* For each commit traversed, call `graph_update()` to move the graph to the
- next commit. Once `graph_update()` has been called, call `graph_next_line()`
- repeatedly, until `graph_is_commit_finished()` returns non-zero. Each call
- to `graph_next_line()` will output a single line of the graph. The resulting
+* For each commit, call `graph_next_line()` repeatedly, until
+ `graph_is_commit_finished()` returns non-zero. Each call go
+ `graph_next_line()` will output a single line of the graph. The resulting
lines will not contain any newlines. `graph_next_line()` returns 1 if the
resulting line contains the current commit, or 0 if this is merely a line
needed to adjust the graph before or after the current commit. This return