--- /dev/null
+#!/bin/sh
+
+test_description='object name disambiguation
+
+Create blobs, trees, commits and a tag that all share the same
+prefix, and make sure "git rev-parse" can take advantage of
+type information to disambiguate short object names that are
+not necessarily unique.
+
+The final history used in the test has five commits, with the bottom
+one tagged as v1.0.0. They all have one regular file each.
+
+ +-------------------------------------------+
+ | |
+ | .-------b3wettvi---- ad2uee |
+ | / / |
+ | a2onsxbvj---czy8f73t--ioiley5o |
+ | |
+ +-------------------------------------------+
+
+'
+
+. ./test-lib.sh
+
+test_expect_success 'blob and tree' '
+ test_tick &&
+ (
+ for i in 0 1 2 3 4 5 6 7 8 9
+ do
+ echo $i
+ done
+ echo
+ echo b1rwzyc3
+ ) >a0blgqsjc &&
+
+ # create one blob 0000000000b36
+ git add a0blgqsjc &&
+
+ # create one tree 0000000000cdc
+ git write-tree
+'
+
+test_expect_success 'warn ambiguity when no candidate matches type hint' '
+ test_must_fail git rev-parse --verify 000000000^{commit} 2>actual &&
+ grep "short SHA1 000000000 is ambiguous" actual
+'
+
+test_expect_failure 'disambiguate tree-ish' '
+ # feed tree-ish in an unambiguous way
+ git rev-parse --verify 0000000000cdc:a0blgqsjc &&
+
+ # ambiguous at the object name level, but there is only one
+ # such tree-ish (the other is a blob)
+ git rev-parse --verify 000000000:a0blgqsjc
+'
+
+test_expect_failure 'disambiguate blob' '
+ sed -e "s/|$//" >patch <<-EOF &&
+ diff --git a/frotz b/frotz
+ index 000000000..ffffff 100644
+ --- a/frotz
+ +++ b/frotz
+ @@ -10,3 +10,4 @@
+ 9
+ |
+ b1rwzyc3
+ +irwry
+ EOF
+ (
+ GIT_INDEX_FILE=frotz &&
+ export GIT_INDEX_FILE &&
+ git apply --build-fake-ancestor frotz patch &&
+ git cat-file blob :frotz >actual
+ ) &&
+ test_cmp a0blgqsjc actual
+'
+
+test_expect_failure 'disambiguate tree' '
+ commit=$(echo "d7xm" | git commit-tree 000000000) &&
+ test $(git rev-parse $commit^{tree}) = $(git rev-parse 0000000000cdc)
+'
+
+test_expect_success 'first commit' '
+ # create one commit 0000000000e4f
+ git commit -m a2onsxbvj
+'
+
+test_expect_failure 'disambiguate commit-ish' '
+ # feed commit-ish in an unambiguous way
+ git rev-parse --verify 0000000000e4f^{commit} &&
+
+ # ambiguous at the object name level, but there is only one
+ # such commit (the others are tree and blob)
+ git rev-parse --verify 000000000^{commit} &&
+
+ # likewise
+ git rev-parse --verify 000000000^0
+'
+
+test_expect_failure 'disambiguate commit' '
+ commit=$(echo "j9xqh" | git commit-tree 0000000000cdc -p 000000000) &&
+ test $(git rev-parse $commit^) = $(git rev-parse 0000000000e4f)
+'
+
+test_expect_failure 'log name1..name2 takes only commit-ishes on both ends' '
+ git log 000000000..000000000 &&
+ git log ..000000000 &&
+ git log 000000000.. &&
+ git log 000000000...000000000 &&
+ git log ...000000000 &&
+ git log 000000000...
+'
+
+test_expect_failure 'rev-parse name1..name2 takes only commit-ishes on both ends' '
+ git rev-parse 000000000..000000000 &&
+ git rev-parse ..000000000 &&
+ git rev-parse 000000000..
+'
+
+test_expect_failure 'git log takes only commit-ish' '
+ git log 000000000
+'
+
+test_expect_failure 'git reset takes only commit-ish' '
+ git reset 000000000
+'
+
+test_expect_success 'first tag' '
+ # create one tag 0000000000f8f
+ git tag -a -m j7cp83um v1.0.0
+'
+
+test_expect_failure 'two semi-ambiguous commit-ish' '
+ # Once the parser becomes ultra-smart, it could notice that
+ # 110282 before ^{commit} name many different objects, but
+ # that only two (HEAD and v1.0.0 tag) can be peeled to commit,
+ # and that peeling them down to commit yield the same commit
+ # without ambiguity.
+ git rev-parse --verify 110282^{commit} &&
+
+ # likewise
+ git log 000000000..000000000 &&
+ git log ..000000000 &&
+ git log 000000000.. &&
+ git log 000000000...000000000 &&
+ git log ...000000000 &&
+ git log 000000000...
+'
+
+test_expect_failure '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
+ git rev-parse --verify 000000000^{tree}
+'
+
+test_expect_success 'parse describe name' '
+ # feed an unambiguous describe name
+ git rev-parse --verify v1.0.0-0-g0000000000e4f &&
+
+ # ambiguous at the object name level, but there is only one
+ # such commit (others are blob, tree and tag)
+ git rev-parse --verify v1.0.0-0-g000000000
+'
+
+test_expect_success 'more history' '
+ # commit 0000000000043
+ git mv a0blgqsjc d12cr3h8t &&
+ echo h62xsjeu >>d12cr3h8t &&
+ git add d12cr3h8t &&
+
+ test_tick &&
+ git commit -m czy8f73t &&
+
+ # commit 00000000008ec
+ git mv d12cr3h8t j000jmpzn &&
+ echo j08bekfvt >>j000jmpzn &&
+ git add j000jmpzn &&
+
+ test_tick &&
+ git commit -m ioiley5o &&
+
+ # commit 0000000005b0
+ git checkout v1.0.0^0 &&
+ git mv a0blgqsjc f5518nwu &&
+
+ for i in h62xsjeu j08bekfvt kg7xflhm
+ do
+ echo $i
+ done >>f5518nwu &&
+ git add f5518nwu &&
+
+ test_tick &&
+ git commit -m b3wettvi &&
+ side=$(git rev-parse HEAD) &&
+
+ # commit 000000000066
+ git checkout master &&
+
+ # If you use recursive, merge will fail and you will need to
+ # clean up a0blgqsjc as well. If you use resolve, merge will
+ # succeed.
+ test_might_fail git merge --no-commit -s recursive $side &&
+ git rm -f f5518nwu j000jmpzn &&
+
+ test_might_fail git rm -f a0blgqsjc &&
+ (
+ git cat-file blob $side:f5518nwu
+ echo j3l0i9s6
+ ) >ab2gs879 &&
+ git add ab2gs879 &&
+
+ test_tick &&
+ git commit -m ad2uee
+
+'
+
+test_expect_failure 'parse describe name taking advantage of generation' '
+ # ambiguous at the object name level, but there is only one
+ # such commit at generation 0
+ git rev-parse --verify v1.0.0-0-g000000000 &&
+
+ # likewise for generation 2 and 4
+ git rev-parse --verify v1.0.0-2-g000000000 &&
+ git rev-parse --verify v1.0.0-4-g000000000
+'
+
+# Note: because rev-parse does not even try to disambiguate based on
+# the generation number, this test currently succeeds for a wrong
+# reason. When it learns to use the generation number, the previous
+# test should succeed, and also this test should fail because the
+# describe name used in the test with generation number can name two
+# commits. Make sure that such a future enhancement does not randomly
+# pick one.
+test_expect_success 'parse describe name not ignoring ambiguity' '
+ # ambiguous at the object name level, and there are two such
+ # commits at generation 1
+ test_must_fail git rev-parse --verify v1.0.0-1-g000000000
+'
+
+test_expect_success 'ambiguous commit-ish' '
+ # Now there are many commits that begin with the
+ # common prefix, none of these should pick one at
+ # random. They all should result in ambiguity errors.
+ test_must_fail git rev-parse --verify 110282^{commit} &&
+
+ # likewise
+ test_must_fail git log 000000000..000000000 &&
+ test_must_fail git log ..000000000 &&
+ test_must_fail git log 000000000.. &&
+ test_must_fail git log 000000000...000000000 &&
+ test_must_fail git log ...000000000 &&
+ test_must_fail git log 000000000...
+'
+
+test_done