worktree: improve find_worktree() documentation

Do a better job of explaining that find_worktree()'s main purpose is to
locate a worktree based upon input from a user which may be some sort of
shorthand for identifying a worktree rather than an actual path. For
instance, one shorthand a user can use to identify a worktree is by
unique path suffix (i.e. given worktrees at paths "foo/bar" and
"foo/baz", the latter can be identified simply as "baz"). The actual
heuristics find_worktree() uses to select a worktree may be expanded in
the future (for instance, one day it may allow worktree selection by
<id> of the .git/worktrees/<id>/ administrative directory), thus the
documentation does not provide a precise description of how matching is
performed, instead leaving it open-ended to allow for future
enhancement.

While at it, drop mention of the non-NULL requirement of `prefix` since
NULL has long been allowed. For instance, prefix_filename() has
explicitly allowed NULL since 116fb64 (prefix_filename: drop length
parameter, 2017-03-20), and find_worktree() itself since e4da43b
(prefix_filename: return newly allocated string, 2017-03-20).

Signed-off-by: Eric Sunshine <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: sunshineco

worktree.h

@@ -44,8 +44,18 @@ int submodule_uses_worktrees(const char *path);
 const char *get_worktree_git_dir(const struct worktree *wt);
 
 /*
- * Search a worktree that can be unambiguously identified by
- * "arg". "prefix" must not be NULL.
+ * Search for the worktree identified unambiguously by `arg` -- typically
+ * supplied by the user via the command-line -- which may be a pathname or some
+ * shorthand uniquely identifying a worktree, thus making it convenient for the
+ * user to specify a worktree with minimal typing. For instance, if the last
+ * component (say, "foo") of a worktree's pathname is unique among worktrees
+ * (say, "work/foo" and "work/bar"), it can be used to identify the worktree
+ * unambiguously.
+ *
+ * `prefix` should be the `prefix` handed to top-level Git commands along with
+ * `argc` and `argv`.
+ *
+ * Return the worktree identified by `arg`, or NULL if not found.
  */
 struct worktree *find_worktree(struct worktree **list,
 			       const char *prefix,