checkout: do not get confused with ambiguous tag/branch names

Although it is not advisable, we have always allowed a branch
and a tag to have the same basename (i.e. it is not illegal to
have refs/heads/frotz and refs/tags/frotz at the same time).
When talking about a specific commit, the interpretation of
'frotz' has always been "use tag and then check branch",
although we warn when ambiguities exist.

However "git checkout $name" is defined to (1) first see if it
matches the branch name, and if so switch to that branch; (2)
otherwise it is an instruction to detach HEAD to point at the
commit named by $name.  We did not follow this definition when
$name appeared under both refs/heads/ and refs/tags/ -- we
switched to the branch but read the tree from the tagged commit,
which was utterly bogus.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-checkout.sh b/git-checkout.sh
index ed7c2c5f6aab338c844329e3ae3d9c7ce003680f..7c5ca3d62f85b78ec82f02c2045435d889c32cdd 100755 (executable)
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -63,12 +63,13 @@ while [ "$#" != "0" ]; do
                                echo "unknown flag $arg"
                                exit 1
                        fi
-                       new="$rev"
                        new_name="$arg"
                        if git-show-ref --verify --quiet -- "refs/heads/$arg"
                        then
+                               rev=$(git-rev-parse --verify "refs/heads/$arg^0")
                                branch="$arg"
                        fi
+                       new="$rev"
                elif rev=$(git-rev-parse --verify "$arg^{tree}" 2>/dev/null)
                then
                        # checking out selected paths from a tree-ish.

diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 5fa6a45577894e05446351fc5076a27accb1fa9f..ed2e9ee3c6fea4767f0aa288dca02825569abedf 100755 (executable)
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -190,4 +190,44 @@ test_expect_success 'checkout to detach HEAD with HEAD^0' '
        fi
 '
 
+test_expect_success 'checkout with ambiguous tag/branch names' '
+
+       git tag both side &&
+       git branch both master &&
+       git reset --hard &&
+       git checkout master &&
+
+       git checkout both &&
+       H=$(git rev-parse --verify HEAD) &&
+       M=$(git show-ref -s --verify refs/heads/master) &&
+       test "z$H" = "z$M" &&
+       name=$(git symbolic-ref HEAD 2>/dev/null) &&
+       test "z$name" = zrefs/heads/both
+
+'
+
+test_expect_success 'checkout with ambiguous tag/branch names' '
+
+       git reset --hard &&
+       git checkout master &&
+
+       git tag frotz side &&
+       git branch frotz master &&
+       git reset --hard &&
+       git checkout master &&
+
+       git checkout tags/frotz &&
+       H=$(git rev-parse --verify HEAD) &&
+       S=$(git show-ref -s --verify refs/heads/side) &&
+       test "z$H" = "z$S" &&
+       if name=$(git symbolic-ref HEAD 2>/dev/null)
+       then
+               echo "Bad -- should have detached"
+               false
+       else
+               : happy
+       fi
+
+'
+
 test_done