Re: [PATCH] Work around ash "alternate value" expansion bug

Ash (used as /bin/sh on many distros) has a shell expansion bug
for the form ${var:+word word}.  The result is a single argument
"word word".  Work around by using ${var:+word} ${var:+word} or
equivalent.

Signed-off-by: Ben Jackson <redacted>
---

I found this by accident while testing another trivial git-am patch.
It was broken about a week ago in git-am.sh by f79d4c8a and one of the
test cases caught it on FreeBSD.

The other instance has been around longer and I found it by grepping.
I added a new testcase (none too exciting) which exposes the problem.
There are more instances of ${x:+alt} which don't have spaces which I
did not touch.

For the curious:

bash on linux:
	$ parent=ok
	$ echo ${parent:+-p $parent}
	-p ok
	$ for i in ${parent:+-p $parent} ; do echo .$i; done
	.-p
	.ok

ash (/bin/sh) on freebsd:
	$ parent=ok
	$ echo ${parent:+-p $parent}
	-p ok
	$ for i in ${parent:+-p $parent} ; do echo .$i; done
	.-p ok

This is probably a bug in ash.  It does expand ${foo:+*} into many words.

 git-am.sh                  |    2 +-
 git-submodule.sh           |    2 +-
 t/t7400-submodule-basic.sh |    8 ++++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/git-am.sh b/git-am.sh
index bfc50c9..e539c60 100755
--- a/git-am.sh
+++ b/git-am.sh

@@ -570,7 +570,7 @@ do
 			GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"
 			export GIT_COMMITTER_DATE
 		fi &&
-		git commit-tree $tree ${parent:+-p $parent} <"$dotest/final-commit"
+		git commit-tree $tree ${parent:+-p} $parent <"$dotest/final-commit"
 	) &&
 	git update-ref -m "$GIT_REFLOG_ACTION: $FIRSTLINE" HEAD $commit $parent ||
 	stop_here $this

diff --git a/git-submodule.sh b/git-submodule.sh
index 7c2e060..bb3766d 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh

@@ -204,7 +204,7 @@ cmd_add()
 	else
 
 		module_clone "$path" "$realrepo" || exit
-		(unset GIT_DIR; cd "$path" && git checkout -f -q ${branch:+-b "$branch" "origin/$branch"}) ||
+		(unset GIT_DIR; cd "$path" && git checkout -f -q ${branch:+-b} ${branch:+"$branch"} ${branch:+"origin/$branch"}) ||