[PATCHv2] Documentation/git-gc.txt: add reference to githooks

[Chris Packham <judge.packham@gmail.com>]

This advertises the existence of the 'pre-auto-gc' hook and adds a cross
reference to where the hook is documented.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
---

I removed the ',if enabled' part from what I suggested on the list. It never
did read quite right to me and I think it just adds confusion to what should be
a simple sentence.

 Documentation/git-gc.txt |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index a9e0882..315f07e 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -137,6 +137,13 @@ If you are expecting some objects to be collected and they aren't, check
 all of those locations and decide whether it makes sense in your case to
 remove those references.
 
+HOOKS
+-----
+
+The 'git gc --auto' command will run the 'pre-auto-gc' hook.  See
+linkgit:githooks[5] for more information.
+
+
 SEE ALSO
 --------
 linkgit:git-prune[1]
-- 
1.7.1