interpret_branch_name: move docstring to header file

We generally put docstrings with function declarations,
because it's the callers who need to know how the function
works. Let's do so for interpret_branch_name().

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 5c035dae5..81c59d4af 100644
--- a/cache.h
+++ b/cache.h
@@ -1292,6 +1292,27 @@ extern char *oid_to_hex_r(char *out, const struct object_id *oid);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
 
+/*
+ * This reads short-hand syntax that not only evaluates to a commit
+ * object name, but also can act as if the end user spelled the name
+ * of the branch from the command line.
+ *
+ * - "@{-N}" finds the name of the Nth previous branch we were on, and
+ *   places the name of the branch in the given buf and returns the
+ *   number of characters parsed if successful.
+ *
+ * - "<branch>@{upstream}" finds the name of the other ref that
+ *   <branch> is configured to merge with (missing <branch> defaults
+ *   to the current branch), and places the name of the branch in the
+ *   given buf and returns the number of characters parsed if
+ *   successful.
+ *
+ * If the input is not of the accepted format, it returns a negative
+ * number to signal an error.
+ *
+ * If the input was ok but there are not N branch switches in the
+ * reflog, it returns 0.
+ */
 extern int interpret_branch_name(const char *str, int len, struct strbuf *);
 extern int get_oid_mb(const char *str, struct object_id *oid);