>From ba77e001b719ff289cf0b1d3dcffd647af6d175d Mon Sep 17 00:00:00 2001
From: Jonathan Ganc <jonganc@gmail.com>
Date: Thu, 30 Mar 2017 23:13:15 -0400
Subject: [PATCH] Use 'git status' in vc-git-status

---
 lisp/vc/vc-git.el | 79 +++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 53 insertions(+), 26 deletions(-)

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 1a3f1bf..ce662fb 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -231,34 +231,61 @@ (defun vc-git--state-code (code)
     (?U 'edited)     ;; FIXME
     (?T 'edited)))   ;; FIXME
 
+(defun vc-git--git-status-to-vc-state (code-list)
+  "Convert a list CODE-LIST of two-letter git status strings to a vc status.
+
+Each element of CODE-LIST comes from the first two characters of
+a line returned by 'git status' and should be passed in the order given by 'git status'. Elements that are nil are simply ignored.
+
+Note that this function may destroy and/or alter `code-list'.
+
+\(It is necessary to allow CODE-LIST to be a list because
+sometimes git status returns multiple lines, e.g. for a file that
+is removed from the index but is present in the HEAD and working
+tree.) "
+  (setq code-list (remq nil code-list))
+  (pcase code-list
+    ('nil 'up-to-date)
+    (`(,code)
+     (pcase code
+       ("!!" 'ignored)
+       ("??" 'unregistered)
+       ;; have only seen this with a file that is only present in the
+       ;; index. let us call this `removed'
+       ("AD" 'removed)
+       (_ (cond
+           ((string-match-p "^[ RD]+$" code) 'removed)
+           ((string-match-p "^[ M]+$" code) 'edited)
+           ((string-match-p "^[ A]+$" code) 'added)
+           ((string-match-p "^[ U]+$" code) 'conflict)
+           (t 'edited)))))
+    ;;  I know of two times when git state returns more than one element,
+    ;;  in both cases returning '("D " "??")':
+    ;;  1. when a file is removed from the index but present in the
+    ;;     HEAD and working tree, the CODE-LIST will be 
+    ;;  2. when a file A is renamed to B in the index and then back to A
+    ;;     in the working tree, the CODE-LIST will be '("??" "RD")
+    ;;  In both these instances, `unregistered' is a reasonable response.
+    (`("D " "??") 'unregistered)
+    ;;  In other cases, let us return `edited'
+    (_ 'edited)))
+
 (defun vc-git-state (file)
   "Git-specific version of `vc-state'."
-  ;; FIXME: This can't set 'ignored or 'conflict yet
-  ;; The 'ignored state could be detected with `git ls-files -i -o
-  ;; --exclude-standard` It also can't set 'needs-update or
-  ;; 'needs-merge. The rough equivalent would be that upstream branch
-  ;; for current branch is in fast-forward state i.e. current branch
-  ;; is direct ancestor of corresponding upstream branch, and the file
-  ;; was modified upstream.  But we can't check that without a network
-  ;; operation.
-  ;; This assumes that status is known to be not `unregistered' because
-  ;; we've been successfully dispatched here from `vc-state', that
-  ;; means `vc-git-registered' returned t earlier once.  Bug#11757
-  (let ((diff (vc-git--run-command-string
-               file "diff-index" "-p" "--raw" "-z" "HEAD" "--")))
-    (if (and diff
-             (string-match ":[0-7]\\{6\\} [0-7]\\{6\\} [0-9a-f]\\{40\\} [0-9a-f]\\{40\\} \\([ADMUT]\\)\0[^\0]+\0\\(.*\n.\\)?"
-                           diff))
-        (let ((diff-letter (match-string 1 diff)))
-          (if (not (match-beginning 2))
-              ;; Empty diff: file contents is the same as the HEAD
-              ;; revision, but timestamps are different (eg, file
-              ;; was "touch"ed).  Update timestamp in index:
-              (prog1 'up-to-date
-                (vc-git--call nil "add" "--refresh" "--"
-                              (file-relative-name file)))
-            (vc-git--state-code diff-letter)))
-      (if (vc-git--empty-db-p) 'added 'up-to-date))))
+  
+  (save-match-data
+    (let* ((default-directory (file-name-directory (expand-file-name file)))
+           (status
+            (vc-git--run-command-string file "status" "--porcelain" "-z"
+                                        "--untracked-files" "--ignored" "--"))
+           code-list)
+      ;; if this code is adapted to parse git-status for a directory, note
+      ;; that a renamed file takes up two null values and needs to be
+      ;; treated slightly more carefully
+      (while (string-match "^\\(..\\)[^\0]+\0\\(\\(?:a\\|[^a]\\)*\\)$" status)
+        (add-to-list 'code-list (match-string 1 status) t 'ignore)
+        (setq status (match-string 2 status)))
+      (vc-git--git-status-to-vc-state code-list))))
 
 (defun vc-git-working-revision (_file)
   "Git-specific version of `vc-working-revision'."
-- 
2.9.3