[PATCH] subtree: die if failed to find existing splits

[Hironao OTSUBO]

When using git-subtree with --squash option, you may not have commits
indicated by git-subtree-split: at hand.

find_existing_splits dies on such situation, but the caller cmd_split
ignored it and produce unwanted output, i.e. a history that does not
contain commits from subproject. This patch fixes it.

Signed-off-by: Hironao OTSUBO <mote...@gmail.com>
---

Notes:
    I know there was a discussion [1] about moving git-subtree development to
    GitHub, but don't know where the actual repository is, so I am sending this
    patch to the mailing list.
    
    [1]: https://public-inbox.org/git/87mv7kf369....@waller.obbligato.org/

 contrib/subtree/git-subtree.sh     |  2 +-
 contrib/subtree/t/t7900-subtree.sh | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index dec085a23..81ad6e716 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -693,7 +693,7 @@ cmd_split () {
        then
                unrevs=
        else
-               unrevs="$(find_existing_splits "$dir" "$revs")"
+               unrevs="$(find_existing_splits "$dir" "$revs")" || die "could 
not find existing splits"
        fi
 
        # We can't restrict rev-list to only $dir here, because some of our
diff --git a/contrib/subtree/t/t7900-subtree.sh 
b/contrib/subtree/t/t7900-subtree.sh
index d05c613c9..fb3d73acf 100755
--- a/contrib/subtree/t/t7900-subtree.sh
+++ b/contrib/subtree/t/t7900-subtree.sh
@@ -493,6 +493,24 @@ test_expect_success 'split "sub dir"/ with --branch for an 
incompatible branch'
        )
 '
 
+next_test
+test_expect_success 'split fails without squashed commits existing' '
+       subtree_test_create_repo "$subtree_test_count" &&
+       subtree_test_create_repo "$subtree_test_count/sub proj" &&
+       test_create_commit "$subtree_test_count" main1 &&
+       test_create_commit "$subtree_test_count/sub proj" sub1 &&
+               commit1=$( cd "$subtree_test_count/sub proj" && git rev-parse 
HEAD ) &&
+       test_create_commit "$subtree_test_count/sub proj" sub2 &&
+       (
+               cd "$subtree_test_count" &&
+               git fetch ./"sub proj" master &&
+               git subtree add --prefix="sub dir" --squash FETCH_HEAD &&
+               git gc --prune=all &&
+               ! git rev-parse -q --verify "$commit1^{commit}" &&
+               test_must_fail git subtree split --prefix="sub dir"
+       )
+'
+
 #
 # Validity checking
 #
-- 
2.16.1