rebase -i: proper prepare-commit-msg hook argument when squashing
rebase -i: proper prepare-commit-msg hook argument when squashing

One would expect that the prepare-commit-msg hook gets 'squash' as the
second argument when squashing commits with 'rebase -i'.  However,
that was not the case, as it got 'merge' instead.  This patch fixes
the problem.

Signed-off-by: SZEDER Gábor <46692b1f0516358b02a6405518c0a52aa8fb3e94@ira.uka.de>
Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git