bug#66464: Vc mode-line

[Juri Linkov]

In order to prepare for making the vc mode-line more customizable,
here is refactoring that helps to avoid code duplication in
vc-hg-mode-line-string, and at the same time makes
vc-git-mode-line-string less hackish while keeping it short.

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 5c21a5b884e..80c79db93ca 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -416,15 +416,22 @@ vc-git--symbolic-ref
 
 (defun vc-git-mode-line-string (file)
   "Return a string for `vc-mode-line' to put in the mode line for FILE."
-  (let* ((rev (vc-working-revision file 'Git))
+  (let* ((backend-name "Git")
+         (state (vc-state file))
+         (status (vc-mode-line-status state))
+         (state-echo (nth 0 status))
+         (face (nth 1 status))
+         (indicator (nth 2 status))
+         (rev (vc-working-revision file 'Git))
          (disp-rev (or (vc-git--symbolic-ref file)
                        (and rev (substring rev 0 7))))
-         (def-ml (vc-default-mode-line-string 'Git file))
-         (help-echo (get-text-property 0 'help-echo def-ml))
-         (face   (get-text-property 0 'face def-ml)))
-    (propertize (concat (substring def-ml 0 4) disp-rev)
-                'face face
-                'help-echo (concat help-echo "\nCurrent revision: " rev))))
+         (state-string (concat backend-name indicator disp-rev)))
+    (propertize
+     state-string
+     'face face
+     'help-echo (concat state-echo " under the " backend-name
+                        " version control system"
+                        "\nCurrent revision: " rev))))
 
 (cl-defstruct (vc-git-extra-fileinfo
             (:copier nil)
diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
index c3e563a1f10..a749a4b02f7 100644
--- a/lisp/vc/vc-hg.el
+++ b/lisp/vc/vc-hg.el
@@ -354,8 +354,10 @@ vc-hg-mode-line-string
   (let* ((backend-name "Hg")
          (truename (file-truename file))
          (state (vc-state truename))
-         (state-echo nil)
-         (face nil)
+         (status (vc-mode-line-status state))
+         (state-echo (nth 0 status))
+         (face (nth 1 status))
+         (indicator (nth 2 status))
          (rev (and state
                    (let ((default-directory
                           (expand-file-name (vc-hg-root truename))))
@@ -363,33 +365,10 @@ vc-hg-mode-line-string
                       "."
                       (and vc-hg-use-file-version-for-mode-line-version
                            truename)))))
-         (rev (or rev "???")))
+         (rev (or rev "???"))
+         (state-string (concat backend-name indicator rev)))
     (propertize
-     (cond ((or (eq state 'up-to-date)
-                (eq state 'needs-update))
-            (setq state-echo "Up to date file")
-            (setq face 'vc-up-to-date-state)
-            (concat backend-name "-" rev))
-           ((eq state 'added)
-            (setq state-echo "Locally added file")
-            (setq face 'vc-locally-added-state)
-            (concat backend-name "@" rev))
-           ((eq state 'conflict)
-            (setq state-echo "File contains conflicts after the last merge")
-            (setq face 'vc-conflict-state)
-            (concat backend-name "!" rev))
-           ((eq state 'removed)
-            (setq state-echo "File removed from the VC system")
-            (setq face 'vc-removed-state)
-            (concat backend-name "!" rev))
-           ((eq state 'missing)
-            (setq state-echo "File tracked by the VC system, but missing from 
the file system")
-            (setq face 'vc-missing-state)
-            (concat backend-name "?" rev))
-           (t
-            (setq state-echo "Locally modified file")
-            (setq face 'vc-edited-state)
-            (concat backend-name ":" rev)))
+     state-string
      'face face
      'help-echo (concat state-echo " under the " backend-name
                         " version control system"))))
diff --git a/lisp/vc/vc-hooks.el b/lisp/vc/vc-hooks.el
index a4de0a6e791..94c3682b4aa 100644
--- a/lisp/vc/vc-hooks.el
+++ b/lisp/vc/vc-hooks.el
@@ -705,6 +733,46 @@ vc-mode-line
   (force-mode-line-update)
   backend)
 
+(defun vc-mode-line-status (state)
+  (let (state-echo face indicator)
+    (cond ((or (eq state 'up-to-date)
+               (eq state 'needs-update))
+           (setq state-echo "Up to date file")
+           (setq face 'vc-up-to-date-state)
+           (setq indicator "-"))
+          ((stringp state)
+           (setq state-echo (concat "File locked by" state))
+           (setq face 'vc-locked-state)
+           (setq indicator (concat ":" state ":")))
+          ((eq state 'added)
+           (setq state-echo "Locally added file")
+           (setq face 'vc-locally-added-state)
+           (setq indicator "@"))
+          ((eq state 'conflict)
+           (setq state-echo "File contains conflicts after the last merge")
+           (setq face 'vc-conflict-state)
+           (setq indicator "!"))
+          ((eq state 'removed)
+           (setq state-echo "File removed from the VC system")
+           (setq face 'vc-removed-state)
+           (setq indicator "!"))
+          ((eq state 'missing)
+           (setq state-echo "File tracked by the VC system, but missing from 
the file system")
+           (setq face 'vc-missing-state)
+           (setq indicator "?"))
+          ((eq state 'ignored)
+           (setq state-echo "File tracked by the VC system, but ignored")
+           (setq face 'vc-ignored-state)
+           (setq indicator "!"))
+          (t
+           ;; Not just for the 'edited state, but also a fallback
+           ;; for all other states.  Think about different symbols
+           ;; for 'needs-update and 'needs-merge.
+           (setq state-echo "Locally modified file")
+           (setq face 'vc-edited-state)
+           (setq indicator ":")))
+    (list state-echo face indicator)))
+
 (defun vc-default-mode-line-string (backend file)
   "Return a string for `vc-mode-line' to put in the mode line for FILE.
 Format:
@@ -718,47 +786,15 @@ vc-default-mode-line-string
 
 This function assumes that the file is registered."
   (let* ((backend-name (symbol-name backend))
-        (state   (vc-state file backend))
-        (state-echo nil)
-        (face nil)
-        (rev     (vc-working-revision file backend)))
+         (state (vc-state file backend))
+         (rev (vc-working-revision file backend))
+         (status (vc-mode-line-status state))
+         (state-echo (nth 0 status))
+         (face (nth 1 status))
+         (indicator (nth 2 status))
+         (state-string (concat backend-name indicator rev)))
     (propertize
-     (cond ((or (eq state 'up-to-date)
-               (eq state 'needs-update))
-           (setq state-echo "Up to date file")
-           (setq face 'vc-up-to-date-state)
-           (concat backend-name "-" rev))
-          ((stringp state)
-           (setq state-echo (concat "File locked by" state))
-           (setq face 'vc-locked-state)
-           (concat backend-name ":" state ":" rev))
-           ((eq state 'added)
-            (setq state-echo "Locally added file")
-           (setq face 'vc-locally-added-state)
-            (concat backend-name "@" rev))
-           ((eq state 'conflict)
-            (setq state-echo "File contains conflicts after the last merge")
-           (setq face 'vc-conflict-state)
-            (concat backend-name "!" rev))
-           ((eq state 'removed)
-            (setq state-echo "File removed from the VC system")
-           (setq face 'vc-removed-state)
-            (concat backend-name "!" rev))
-           ((eq state 'missing)
-            (setq state-echo "File tracked by the VC system, but missing from 
the file system")
-           (setq face 'vc-missing-state)
-            (concat backend-name "?" rev))
-           ((eq state 'ignored)
-            (setq state-echo "File tracked by the VC system, but ignored")
-            (setq face 'vc-ignored-state)
-            (concat backend-name "!" rev))
-          (t
-           ;; Not just for the 'edited state, but also a fallback
-           ;; for all other states.  Think about different symbols
-           ;; for 'needs-update and 'needs-merge.
-           (setq state-echo "Locally modified file")
-           (setq face 'vc-edited-state)
-           (concat backend-name ":" rev)))
+     state-string
      'face face
      'help-echo (concat state-echo " under the " backend-name
                        " version control system"))))