stash: learn to parse -m/--message like commit does

[Phil Hord <phil.hord@gmail.com>]

`git stash push -m foo` uses "foo" as the message for the stash. But
`git stash push -m"foo"` does not parse successfully.  Similarly
`git stash push --message="My stash message"` also fails.  Nothing
in the documentation suggests this syntax should work, but it does
work for `git commit`, and my fingers have learned this pattern long
ago.

Teach `git stash` to parse -mFoo and --message=Foo the same as
`git commit` would do.

Signed-off-by: Phil Hord <phil.hord@gmail.com>
---
 git-stash.sh | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/git-stash.sh b/git-stash.sh
index 4b7495144..1114005ce 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -76,6 +76,12 @@ create_stash () {
  shift
  stash_msg=${1?"BUG: create_stash () -m requires an argument"}
  ;;
+ -m*)
+ stash_msg=${1#-m}
+ ;;
+ --message=*)
+ stash_msg=${1#--message=}
+ ;;
  -u|--include-untracked)
  shift
  untracked=${1?"BUG: create_stash () -u requires an argument"}
@@ -193,6 +199,12 @@ store_stash () {
  shift
  stash_msg="$1"
  ;;
+ -m*)
+ stash_msg=${1#-m}
+ ;;
+ --message=*)
+ stash_msg=${1#--message=}
+ ;;
  -q|--quiet)
  quiet=t
  ;;
@@ -251,6 +263,12 @@ push_stash () {
  test -z ${1+x} && usage
  stash_msg=$1
  ;;
+ -m*)
+ stash_msg=${1#-m}
+ ;;
+ --message=*)
+ stash_msg=${1#--message=}
+ ;;
  --help)
  show_help
  ;;
-- 
2.15.0.471.g17a719cfe.dirty