t1507: add tests to document @{upstream} behaviour

In preparation for future changes, add tests which show error messages
with @{upstream} in various conditions:

- test branch@{u} with . as remote
- check error message for branch@{u} on a branch with
  * no upstream,
  * on a branch with a configured upstream which doesn't have a
    remote-tracking branch
- check error message for branch@{u} when branch 'branch' does not
  exist
- check error message for @{u} without the branch name

Right now the messages are very similar, but various cases can and
will be distinguished.

Note: test_i18ncmp is not used, because currently error output is not
internationalized. test_cmp will be switched to test_i18ncmp in a later
patch, when error messages are internationalized.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1507-rev-parse-upstream.sh

@@ -15,10 +15,18 @@ test_expect_success 'setup' '
 	test_commit 3 &&
 	(cd clone &&
 	 test_commit 4 &&
-	 git branch --track my-side origin/side)
-
+	 git branch --track my-side origin/side &&
+	 git branch --track local-master master &&
+	 git remote add -t master master-only .. &&
+	 git fetch master-only &&
+	 git branch bad-upstream &&
+	 git config branch.bad-upstream.remote master-only &&
+	 git config branch.bad-upstream.merge refs/heads/side
+	)
 '
 
+sq="'"
+
 full_name () {
 	(cd clone &&
 	 git rev-parse --symbolic-full-name "$@")
@@ -29,6 +37,11 @@ commit_subject () {
 	 git show -s --pretty=format:%s "$@")
 }
 
+error_message () {
+	(cd clone &&
+	 test_must_fail git rev-parse --verify "$@")
+}
+
 test_expect_success '@{upstream} resolves to correct full name' '
 	test refs/remotes/origin/master = "$(full_name @{upstream})"
 '
@@ -78,7 +91,6 @@ test_expect_success 'checkout -b new my-side@{u} forks from the same' '
 
 test_expect_success 'merge my-side@{u} records the correct name' '
 (
-	sq="'\''" &&
 	cd clone || exit
 	git checkout master || exit
 	git branch -D new ;# can fail but is ok
@@ -107,6 +119,69 @@ test_expect_success 'checkout other@{u}' '
 	test_cmp expect actual
 '
 
+test_expect_success 'branch@{u} works when tracking a local branch' '
+	test refs/heads/master = "$(full_name local-master@{u})"
+'
+
+test_expect_success 'branch@{u} error message when no upstream' '
+	cat >expect <<-EOF &&
+	error: No upstream branch found for ${sq}non-tracking${sq}
+	fatal: Needed a single revision
+	EOF
+	error_message non-tracking@{u} 2>actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '@{u} error message when no upstream' '
+	cat >expect <<-EOF &&
+	error: No upstream branch found for ${sq}${sq}
+	fatal: Needed a single revision
+	EOF
+	test_must_fail git rev-parse --verify @{u} 2>actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'branch@{u} error message with misspelt branch' '
+	cat >expect <<-EOF &&
+	error: No upstream branch found for ${sq}no-such-branch${sq}
+	fatal: Needed a single revision
+	EOF
+	error_message no-such-branch@{u} 2>actual &&
+	test_cmp expect actual
+'
+
+test_expect_success '@{u} error message when not on a branch' '
+	cat >expect <<-EOF &&
+	error: No upstream branch found for ${sq}${sq}
+	fatal: Needed a single revision
+	EOF
+	git checkout HEAD^0 &&
+	test_must_fail git rev-parse --verify @{u} 2>actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'branch@{u} error message if upstream branch not fetched' '
+	cat >expect <<-EOF &&
+	error: No upstream branch found for ${sq}bad-upstream${sq}
+	fatal: Needed a single revision
+	EOF
+	error_message bad-upstream@{u} 2>actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pull works when tracking a local branch' '
+(
+	cd clone &&
+	git checkout local-master &&
+	git pull
+)
+'
+
+# makes sense if the previous one succeeded
+test_expect_success '@{u} works when tracking a local branch' '
+	test refs/heads/master = "$(full_name @{u})"
+'
+
 cat >expect <<EOF
 commit 8f489d01d0cc65c3b0f09504ec50b5ed02a70bd5
 Reflog: master@{0} (C O Mitter <committer@example.com>)