Test more vc-dir scenarios with Git (bug#68183)

* test/lisp/vc/vc-git-tests.el
(vc-git-test-dir-track-local-branch): Remove in favor of new
test.
(vc-git-test--start-branch): New helper to get a repository
going.
(vc-git-test--dir-headers): New helper to get a list of headers
in the current vc-dir buffer.
(vc-git-test-dir-branch-headers): New test, exercising the
original bug recipe plus more common scenarios.

test/lisp/vc/vc-git-tests.el

@@ -26,6 +26,7 @@
 
 (require 'ert-x)
 (require 'vc)
+(require 'vc-dir)
 (require 'vc-git)
 
 (ert-deftest vc-git-test-program-version-general ()
@@ -108,24 +109,85 @@ allow `git commit' to determine identities for authors and committers."
     (apply 'vc-git-command t 0 nil args)
     (buffer-string)))
 
-(ert-deftest vc-git-test-dir-track-local-branch ()
-  "Test that `vc-dir' works when tracking local branches.  Bug#68183."
+(defun vc-git-test--start-branch ()
+  "Get a branch started in a freshly initialized repository.
+
+This returns the name of the current branch, so that tests can remain
+agnostic of init.defaultbranch."
+  (write-region "hello" nil "README")
+  (vc-git-test--run "add" "README")
+  (vc-git-test--run "commit" "-mFirst")
+  (string-trim (vc-git-test--run "branch" "--show-current")))
+
+(defun vc-git-test--dir-headers (headers)
+  "Return an alist of header values for the current `vc-dir' buffer.
+
+HEADERS should be a list of (NAME ...) strings.  This function will
+return a list of (NAME . VALUE) pairs, where VALUE is nil if the header
+is absent."
+  ;; FIXME: to reproduce interactive sessions faithfully, we would need
+  ;; to wait for the dir-status-files process to terminate; have not
+  ;; found a reliable way to do this.  As a workaround, kill pending
+  ;; processes and revert the `vc-dir' buffer.
+  (vc-dir-kill-dir-status-process)
+  (revert-buffer)
+  (mapcar
+   (lambda (header)
+     (let* ((pattern
+             (rx bol
+                 (literal header) (* space) ": " (group (+ nonl))
+                 eol))
+            (value (and (goto-char (point-min))
+                        (re-search-forward pattern nil t)
+                        (match-string 1))))
+       (cons header value)))
+   headers))
+
+(ert-deftest vc-git-test-dir-branch-headers ()
+  "Check that `vc-dir' shows expected branch-related headers."
   (skip-unless (executable-find vc-git-program))
-  (vc-git-test--with-repo repo
-    ;; Create an initial commit to get a branch started.
-    (write-region "hello" nil "README")
-    (vc-git-test--run "add" "README")
-    (vc-git-test--run "commit" "-mFirst")
-    ;; Get current branch name lazily, to remain agnostic of
-    ;; init.defaultbranch.
-    (let ((upstream-branch
-           (string-trim (vc-git-test--run "branch" "--show-current"))))
-      (vc-git-test--run "checkout" "--track" "-b" "hack" upstream-branch)
-      (vc-dir default-directory)
-      (pcase-dolist (`(,header ,value)
-                     `(("Branch" "hack")
-                       ("Tracking" ,upstream-branch)))
-        (goto-char (point-min))
-        (re-search-forward (format "^%s *: %s$" header value))))))
+  ;; Create a repository that will serve as the "remote".
+  (vc-git-test--with-repo origin-repo
+    (let ((main-branch (vc-git-test--start-branch)))
+      ;; 'git clone' this repository and test things in this clone.
+      (ert-with-temp-directory clone-repo
+        (vc-git-test--run "clone" origin-repo clone-repo)
+        (vc-dir clone-repo)
+        (should
+         (equal
+          (vc-git-test--dir-headers
+           '("Branch" "Tracking" "Remote"))
+          `(("Branch"   . ,main-branch)
+            ("Tracking" . ,(concat "origin/" main-branch))
+            ("Remote"   . ,origin-repo))))
+        ;; Checkout a new branch: no tracking information.
+        (vc-git-test--run "checkout" "-b" "feature/foo" main-branch)
+        (should
+         (equal
+          (vc-git-test--dir-headers
+           '("Branch" "Tracking" "Remote"))
+          '(("Branch"   . "feature/foo")
+            ("Tracking" . nil)
+            ("Remote"   . nil))))
+        ;; Push with '--set-upstream origin': tracking information
+        ;; should be updated.
+        (vc-git-test--run "push" "--set-upstream" "origin" "feature/foo")
+        (should
+         (equal
+          (vc-git-test--dir-headers
+           '("Branch" "Tracking" "Remote"))
+          `(("Branch"   . "feature/foo")
+            ("Tracking" . "origin/feature/foo")
+            ("Remote"   . ,origin-repo))))
+        ;; Checkout a new branch tracking the _local_ main branch.
+        ;; Bug#68183.
+        (vc-git-test--run "checkout" "-b" "feature/bar" "--track" main-branch)
+        (should
+         (equal
+          (vc-git-test--dir-headers
+           '("Branch" "Tracking" "Remote"))
+          `(("Branch"   . "feature/bar")
+            ("Tracking" . ,main-branch)
+            ("Remote"   . "none (tracking local branch)"))))))))
 
 ;;; vc-git-tests.el ends here