[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"}) ||
 		die "Unable to checkout submodule '$path'"
 	fi
 

diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index af690ec..3c05c27 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh

@@ -64,6 +64,14 @@ test_expect_success 'submodule add' '
 	)
 '
 
+test_expect_success 'submodule add --branch' '
+	(
+		cd addtest &&
+		git submodule add -b initial "$submodurl" submod-branch &&
+		git submodule init
+	)
+'
+
 test_expect_success 'submodule add with ./ in path' '
 	(
 		cd addtest &&

-- 
1.6.0.1

Ben Jackson [off-list ref] writes:

I do not mind this one, but

this is too ugly to live in our codebase, and without an accompanying code
comment, I am sure somebody (if not myself) will "fix" it again.

	(
        	unset GIT_DIR
		cd "$path" &&
		# BSD ash mishandles ${branch:+-b "$branch" ...}, sheesh.
                case "$branch" in
                '')	git checkout -f -q ;;
                ?*)	git checkout -f -q -b "$branch" "origin/$branch" ;;
                esac
	) ||
	...

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>
---

See http://thread.gmane.org/gmane.comp.version-control.git/116816 for
the original notes which describe the problem in more detail.

This version uses a different workaround suggested by Junio for
git-submodule which is less likely to be "cleaned up" back to the
original problem.  Since new the change is more complex I beefed
up the new test slightly to ensure we are getting into the right case.

 git-am.sh                  |    2 +-
 git-submodule.sh           |   11 +++++++++--
 t/t7400-submodule-basic.sh |   10 ++++++++++
 3 files changed, 20 insertions(+), 3 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..8e234a4 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh

@@ -204,8 +204,15 @@ cmd_add()
 	else
 
 		module_clone "$path" "$realrepo" || exit
-		(unset GIT_DIR; cd "$path" && git checkout -f -q ${branch:+-b "$branch" "origin/$branch"}) ||
-		die "Unable to checkout submodule '$path'"
+		(
+			unset GIT_DIR
+			cd "$path" &&
+			# ash fails to wordsplit ${branch:+-b "$branch"...}
+			case "$branch" in
+			'') git checkout -f -q ;;
+			?*) git checkout -f -q -b "$branch" "origin/$branch" ;;
+			esac
+		) || die "Unable to checkout submodule '$path'"
 	fi
 
 	git add "$path" ||

diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index af690ec..0f2ccc6 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh

@@ -64,6 +64,16 @@ test_expect_success 'submodule add' '
 	)
 '
 
+test_expect_success 'submodule add --branch' '
+	(
+		cd addtest &&
+		git submodule add -b initial "$submodurl" submod-branch &&
+		git submodule init &&
+		cd submod-branch &&
+		git branch | grep initial
+	)
+'
+
 test_expect_success 'submodule add with ./ in path' '
 	(
 		cd addtest &&

-- 
1.6.0.1