[PATCH 7/9] get_short_oid / peel_onion: ^{tree} should mean tree, not treeish

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

After the recent series of patches ^{tag} and ^{blob} now work to get
just the tags and blobs, but ^{tree} will still list any
tree-ish (commits, tags and trees).

The previous behavior was added in ed1ca6025f ("peel_onion:
disambiguate to favor tree-ish when we know we want a tree-ish",
2013-03-31). I may have missed some special-case but this makes more
sense to me.

Now "$sha1:" can be used as before to mean treeish

    $ git rev-parse e8f2:
    error: short SHA1 e8f2 is ambiguous
    hint: The candidates are:
    hint:   e8f2650052 tag v2.17.0
    hint:   e8f21caf94 commit 2013-06-24 - bash prompt: print unique detached HEAD abbreviated object name
    hint:   e8f26250fa commit 2017-02-03 - Merge pull request #996 from jeffhostetler/jeffhostetler/register_rename_src
    hint:   e8f2bc0c06 commit 2015-05-10 - Documentation: note behavior for multiple remote.url entries
    hint:   e8f2093055 tree
    hint:   e8f25a3a50 tree
    hint:   e8f28d537c tree
    hint:   e8f2cf6ec0 tree
    [...]

But ^{tree} shows just the trees, but would previously be equivalent
to the above:

    $ git rev-parse e8f2^{tree}
    error: short SHA1 e8f2 is ambiguous
    hint: The candidates are:
    hint:   e8f2093055 tree
    hint:   e8f25a3a50 tree
    hint:   e8f28d537c tree
    hint:   e8f2cf6ec0 tree
    [...]

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 sha1-name.c                         |  2 +-
 t/t1512-rev-parse-disambiguation.sh | 18 ++++++++++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/sha1-name.c b/sha1-name.c
index 023f9471a8..b61c0558d9 100644
--- a/sha1-name.c
+++ b/sha1-name.c
@@ -970,7 +970,7 @@ static int peel_onion(const char *name, int len, struct object_id *oid,
 	else if (expected_type == OBJ_TAG)
 		lookup_flags |= GET_OID_TAG;
 	else if (expected_type == OBJ_TREE)
-		lookup_flags |= GET_OID_TREEISH;
+		lookup_flags |= GET_OID_TREE;
 	else if (expected_type == OBJ_BLOB)
 		lookup_flags |= GET_OID_BLOB;
 
diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
index 08ae73e2a5..2acf564714 100755
--- a/t/t1512-rev-parse-disambiguation.sh
+++ b/t/t1512-rev-parse-disambiguation.sh
@@ -159,9 +159,13 @@ test_expect_failure 'two semi-ambiguous commit-ish' '
 	git log 0000000000...
 '
 
-test_expect_failure 'three semi-ambiguous tree-ish' '
+test_expect_success 'three semi-ambiguous tree-ish' '
 	# Likewise for tree-ish.  HEAD, v1.0.0 and HEAD^{tree} share
 	# the prefix but peeling them to tree yields the same thing
+	test_must_fail git rev-parse --verify 0000000000: &&
+
+	# For ^{tree} we can disambiguate because HEAD and v1.0.0 will
+	# be excluded.
 	git rev-parse --verify 0000000000^{tree}
 '
 
@@ -267,8 +271,12 @@ test_expect_success 'ambiguous commit-ish' '
 # There are three objects with this prefix: a blob, a tree, and a tag. We know
 # the blob will not pass as a treeish, but the tree and tag should (and thus
 # cause an error).
-test_expect_success 'ambiguous tags peel to treeish' '
-	test_must_fail git rev-parse 0000000000f^{tree}
+test_expect_success 'ambiguous tags peel to treeish or tree' '
+	test_must_fail git rev-parse 0000000000f: &&
+	git rev-parse 0000000000f^{tree} >stdout &&
+	test_line_count = 1 stdout &&
+	grep -q ^0000000000fd8bcc56 stdout
+
 '
 
 test_expect_success 'rev-parse --disambiguate' '
@@ -365,7 +373,9 @@ test_expect_success 'core.disambiguate config can prefer types' '
 test_expect_success 'core.disambiguate does not override context' '
 	# treeish ambiguous between tag and tree
 	test_must_fail \
-		git -c core.disambiguate=committish rev-parse $sha1^{tree}
+		git -c core.disambiguate=committish rev-parse $sha1: &&
+	# tree not ambiguous between tag and tree
+	git -c core.disambiguate=committish rev-parse $sha1^{tree}
 '
 
 test_done
-- 
2.17.0.290.gded63e768a