Subject: [PATCH v2] branch: segfault fixes and validation

From: Nguyễn Thái Ngọc Duy <[email-masked]>
Date: Fri, 22 Feb 2013 18:47:43 +0700

branch_get() can return NULL (so far on detached HEAD only) but some
code paths in builtin/branch.c cannot deal with that and cause
segfaults. While at there, make sure we bail out when the user gives 2
or more arguments, but we only process the first one and silently
ignore the rest.

Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
---
 On Fri, Feb 22, 2013 at 12:47 AM, Junio C Hamano <[email-masked]> wrote:
 > Nguyễn Thái Ngọc Duy  <[email-masked]> writes:
 >
 >> branch_get() can return NULL (so far on detached HEAD only)...
 >
 > Do you anticipate any other cases where the API call should validly
 > return NULL?
 
 No. But I do not see any guarantee that it may never do that in
 future either. Which is why I was deliberately vague with "could not
 figure out...". But you also correctly observed my laziness there. So
 how about this? It makes a special case for HEAD but not insist on
 detached HEAD as the only cause.

 builtin/branch.c  | 24 ++++++++++++++++++++++++
 t/t3200-branch.sh | 21 +++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/builtin/branch.c b/builtin/branch.c
index 6371bf9..82ed337 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -889,6 +889,15 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	} else if (new_upstream) {
 		struct branch *branch = branch_get(argv[0]);
 
+		if (argc > 1)
+			die(_("too many branches to set new upstream"));
+
+		if (!branch) {
+			if (!argc || !strcmp(argv[0], "HEAD"))
+				die(_("HEAD does not point to any branch. Is it detached?"));
+			die(_("no such branch '%s'"), argv[0]);
+		}
+
 		if (!ref_exists(branch->refname))
 			die(_("branch '%s' does not exist"), branch->name);
 
@@ -901,6 +910,15 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		struct branch *branch = branch_get(argv[0]);
 		struct strbuf buf = STRBUF_INIT;
 
+		if (argc > 1)
+			die(_("too many branches to unset upstream"));
+
+		if (!branch) {
+			if (!argc || !strcmp(argv[0], "HEAD"))
+				die(_("HEAD does not point to any branch. Is it detached?"));
+			die(_("no such branch '%s'"), argv[0]);
+		}
+
 		if (!branch_has_merge_config(branch)) {
 			die(_("Branch '%s' has no upstream information"), branch->name);
 		}
@@ -916,6 +934,12 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		int branch_existed = 0, remote_tracking = 0;
 		struct strbuf buf = STRBUF_INIT;
 
+		if (!strcmp(argv[0], "HEAD"))
+			die(_("it does not make sense to create 'HEAD' manually"));
+
+		if (!branch)
+			die(_("no such branch '%s'"), argv[0]);
+
 		if (kinds != REF_LOCAL_BRANCH)
 			die(_("-a and -r options to 'git branch' do not make sense with a branch name"));
 
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index f3e0e4a..12f1e4a 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -42,6 +42,10 @@ test_expect_success \
     'git branch a/b/c should create a branch' \
     'git branch a/b/c && test_path_is_file .git/refs/heads/a/b/c'
 
+test_expect_success \
+    'git branch HEAD should fail' \
+    'test_must_fail git branch HEAD'
+
 cat >expect <<EOF
 $_z40 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master
 EOF
@@ -388,6 +392,14 @@ test_expect_success \
     'git tag foobar &&
      test_must_fail git branch --track my11 foobar'
 
+test_expect_success '--set-upstream-to fails on multiple branches' \
+    'test_must_fail git branch --set-upstream-to master a b c'
+
+test_expect_success '--set-upstream-to fails on detached HEAD' \
+    'git checkout HEAD^{} &&
+     test_must_fail git branch --set-upstream-to master &&
+     git checkout -'
+
 test_expect_success 'use --set-upstream-to modify HEAD' \
     'test_config branch.master.remote foo &&
      test_config branch.master.merge foo &&
@@ -417,6 +429,15 @@ test_expect_success 'test --unset-upstream on HEAD' \
      test_must_fail git branch --unset-upstream
 '
 
+test_expect_success '--unset-upstream should fail on multiple branches' \
+    'test_must_fail git branch --unset-upstream a b c'
+
+test_expect_success '--unset-upstream should fail on detached HEAD' \
+    'git checkout HEAD^{} &&
+     test_must_fail git branch --unset-upstream &&
+     git checkout -
+'
+
 test_expect_success 'test --unset-upstream on a particular branch' \
     'git branch my15
      git branch --set-upstream-to master my14 &&
-- 
1.8.1.2.536.gf441e6d