completion: find out supported merge strategies correctly

"git-merge" is a binary executable these days, and looking for assignment
to $all_strategies variable with grep/sed does not work well.

When asked for an unknown strategy, pre-1.6.0 and post-1.6.0 "git merge"
commands respectively say:

    $ $HOME/git-snap-v1.5.6.5/bin/git merge -s help
    available strategies are: recur recursive octopus resolve stupid ours subtree
    $ $HOME/git-snap-v1.6.0/bin/git merge -s help
    Could not find merge strategy 'help'.
    Available strategies are: recursive octopus resolve ours subtree.

both on their standard error stream.  We can use this to learn what
strategies are supported.

The sed script is written in such a way that it catches both old and new
message styles ("Available" vs "available", and the full stop at the end).
It also allows future versions of "git merge" to line-wrap the list of
strategies, and add extra comments, like this:

    $ $HOME/git-snap-v1.6.1/bin/git merge -s help
    Could not find merge strategy 'help'.
    Available strategies are: blame recursive octopus resolve ours
    subtree.
    Also you have custom strategies: theirs

    Make sure you spell strategy names correctly.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 158b91284147d50a24d6dadaa7c5085cf0b7cb55..a31004088a969a231972267333ee1cafa1d47233 100755 (executable)
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -271,15 +271,17 @@ __git_merge_strategies ()
                echo "$__git_merge_strategylist"
                return
        fi
-       sed -n "/^all_strategies='/{
-               s/^all_strategies='//
-               s/'//
+       git merge -s help 2>&1 |
+       sed -n -e '/[Aa]vailable strategies are: /,/^$/{
+               s/\.$//
+               s/.*://
+               s/^[    ]*//
+               s/[     ]*$//
                p
-               q
-               }" "$(git --exec-path)/git-merge"
+       }'
 }
 __git_merge_strategylist=
-__git_merge_strategylist="$(__git_merge_strategies 2>/dev/null)"
+__git_merge_strategylist=$(__git_merge_strategies 2>/dev/null)
 
 __git_complete_file ()
 {