[PATCH] builtin-remote: make rm operation safer in mirrored repository

[Jay Soffian <jaysoffian@gmail.com>]

"git remote rm <repo>" is happy to remove non-remote branches (and their
reflogs). This may be okay if the repository truely is a mirror, but if the
user had done "git remote add --mirror <repo>" by accident and was just
undoing their mistake, then they are left in a situation that is difficult to
recover from.

After this commit, "git remote rm" skips over non-remote branches and instead
advises the user on how to remove such branches using "git branch -d", which
itself has nice safety checks wrt to branch removal lacking from "git remote
rm".

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
---
This version adds a test case. I also noticed that the check I'd added to
add_branch_for_removal() was generating spurious warnings because I'd added it
in the wrong place; this version moves the check below the
remote_find_tracking() checks.

 builtin-remote.c  |    7 +++++++
 t/t5505-remote.sh |    9 +++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/builtin-remote.c b/builtin-remote.c
index abc8dd8..571caff 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -323,6 +323,13 @@ static int add_branch_for_removal(const char *refname,
 			return 0;
 	}
 
+	/* don't delete non-remote branches */
+	if (prefixcmp(refname, "refs/remotes")) {
+		warning("not removing non-remote branch; use git branch -d %s to remove",
+			abbrev_branch(refname));
+		return 0;
+	}
+
 	/* make sure that symrefs are deleted */
 	if (flags & REF_ISSYMREF)
 		return unlink(git_path("%s", refname));
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index 1f59960..80d40ea 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -107,6 +107,15 @@ test_expect_success 'remove remote' '
 )
 '
 
+test_expect_success 'remove remote protects non-remote branches' '
+(
+	cd test &&
+	git config --add remote.oops.fetch "+refs/*:refs/*" &&
+	git remote rm oops 2>stderr &&
+	grep "not removing non-remote branch.* master " stderr
+)
+'
+
 cat > test/expect << EOF
 * remote origin
   URL: $(pwd)/one
-- 
1.6.1.2.308.gd57ba