builtin-remote: make rm operation safer in mirrored repository

"git remote rm <repo>" happily removes non-remote refs 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 refs. The user
is advised on how remove branches using "git branch -d", which itself
has nice safety checks wrt to branch removal lacking from "git remote rm".
Non-remote non-branch refs are skipped silently.

Signed-off-by: Jay Soffian <jaysoffian@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-remote.c

@@ -296,7 +296,7 @@ static int add_known_remote(struct remote *remote, void *cb_data)
 
 struct branches_for_remote {
 	struct remote *remote;
-	struct string_list *branches;
+	struct string_list *branches, *skipped;
 	struct known_remotes *keep;
 };
 
@@ -321,6 +321,16 @@ static int add_branch_for_removal(const char *refname,
 			return 0;
 	}
 
+	/* don't delete non-remote refs */
+	if (prefixcmp(refname, "refs/remotes")) {
+		/* advise user how to delete local branches */
+		if (!prefixcmp(refname, "refs/heads/"))
+			string_list_append(abbrev_branch(refname),
+					   branches->skipped);
+		/* silently skip over other non-remote refs */
+		return 0;
+	}
+
 	/* make sure that symrefs are deleted */
 	if (flags & REF_ISSYMREF)
 		return unlink(git_path("%s", refname));
@@ -355,7 +365,10 @@ static int rm(int argc, const char **argv)
 	struct strbuf buf;
 	struct known_remotes known_remotes = { NULL, NULL };
 	struct string_list branches = { NULL, 0, 0, 1 };
-	struct branches_for_remote cb_data = { NULL, &branches, &known_remotes };
+	struct string_list skipped = { NULL, 0, 0, 1 };
+	struct branches_for_remote cb_data = {
+		NULL, &branches, &skipped, &known_remotes
+	};
 	int i, result;
 
 	if (argc != 2)
@@ -404,6 +417,18 @@ static int rm(int argc, const char **argv)
 		result = remove_branches(&branches);
 	string_list_clear(&branches, 1);
 
+	if (skipped.nr) {
+		fprintf(stderr, skipped.nr == 1 ?
+			"Note: A non-remote branch was not removed; "
+			"to delete it, use:\n" :
+			"Note: Non-remote branches were not removed; "
+			"to delete them, use:\n");
+		for (i = 0; i < skipped.nr; i++)
+			fprintf(stderr, "  git branch -d %s\n",
+				skipped.items[i].string);
+	}
+	string_list_clear(&skipped, 0);
+
 	return result;
 }
 

t/t5505-remote.sh

@@ -107,6 +107,32 @@ test_expect_success 'remove remote' '
 )
 '
 
+test_expect_success 'remove remote protects non-remote branches' '
+(
+	cd test &&
+	(cat >expect1 <<EOF
+Note: A non-remote branch was not removed; to delete it, use:
+  git branch -d master
+EOF
+    cat >expect2 <<EOF
+Note: Non-remote branches were not removed; to delete them, use:
+  git branch -d foobranch
+  git branch -d master
+EOF
+) &&
+	git tag footag
+	git config --add remote.oops.fetch "+refs/*:refs/*" &&
+	git remote rm oops 2>actual1 &&
+	git branch foobranch &&
+	git config --add remote.oops.fetch "+refs/*:refs/*" &&
+	git remote rm oops 2>actual2 &&
+	git branch -d foobranch &&
+	git tag -d footag &&
+	test_cmp expect1 actual1 &&
+	test_cmp expect2 actual2
+)
+'
+
 cat > test/expect << EOF
 * remote origin
   URL: $(pwd)/one