[RFC v2 11/16] Add explanatory comment for transport-helpers refs mapping.

[Florian Achleitner <florian.achleitner.2.6.31@gmail.com>]

transport-helpers can advertise the 'refspec' capability,
if not a default refspec *:* is assumed. This explains
the post-processing of refs after fetching with fast-import.

Signed-off-by: Florian Achleitner <florian.achleitner.2.6.31@gmail.com>
---
 transport-helper.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/transport-helper.c b/transport-helper.c
index d6daad5..e10fd6b 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -478,6 +478,21 @@ static int fetch_with_import(struct transport *transport,
 
 	argv_array_clear(&importer_argv);
 
+	/*
+	 * If the remote helper advertised the "refspec" capability,
+	 * it will have the written result of the import to the refs
+	 * named on the right hand side of the first refspec matching
+	 * each ref we were fetching.
+	 *
+	 * (If no "refspec" capability was specified, for historical
+	 * reasons we default to *:*.)
+	 *
+	 * Store the result in to_fetch[i].old_sha1.  Callers such
+	 * as "git fetch" can use the value to write feedback to the
+	 * terminal, populate FETCH_HEAD, and determine what new value
+	 * should be written to peer_ref if the update is a
+	 * fast-forward or this is a forced update.
+	 */
 	for (i = 0; i < nr_heads; i++) {
 		char *private;
 		posn = to_fetch[i];
-- 
1.7.9.5