master e4669e0f77 1/2: vc-git: Don't assume .git is a directory

[Sean Whitton]

branch: master
commit e4669e0f77bd982bd9254eaf6f4660181dc0b490
Author: Sean Whitton <spwhitton@spwhitton.name>
Commit: Sean Whitton <spwhitton@spwhitton.name>

    vc-git: Don't assume .git is a directory
    
    * lisp/vc/vc-git.el (vc-git--git-path): New function.
    (vc-git-dir-extra-headers)
    (vc-git-merge-branch)
    (vc-git-resolve-when-done): Use it.
---
 lisp/vc/vc-git.el | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 671be66bbe..92d2eb7f41 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -315,6 +315,23 @@ Good example of file name that needs this: 
\"test[56].xx\".")
                   (string-trim-right (match-string 1 version-string) "\\.")
                 "0")))))
 
+(defun vc-git--git-path (&optional path)
+  "Resolve .git/PATH for the current working tree.
+In particular, handle the case where this is a linked working
+tree, such that .git is a plain file.
+
+See the --git-dir and --git-path options to git-rev-parse(1)."
+  (if (and path (not (string-empty-p path)))
+      ;; Canonicalize in this branch because --git-dir always returns
+      ;; an absolute file name.
+      (expand-file-name
+       (string-trim-right
+        (vc-git--run-command-string nil "rev-parse"
+                                    "--git-path" path)))
+    (concat (string-trim-right
+             (vc-git--run-command-string nil "rev-parse" "--git-dir"))
+            "/")))
+
 (defun vc-git--git-status-to-vc-state (code-list)
   "Convert CODE-LIST to a VC status.
 
@@ -765,6 +782,7 @@ or an empty string if none."
                  (vc-git--out-ok "symbolic-ref" "HEAD"))))
        (stash-list (vc-git-stash-list))
         (default-directory dir)
+        (gitdir (vc-git--git-path))
 
        branch remote remote-url stash-button stash-string)
     (if (string-match "^\\(refs/heads/\\)?\\(.+\\)$" str)
@@ -839,9 +857,9 @@ or an empty string if none."
        (propertize remote-url
                    'face 'vc-dir-header-value)))
      ;; For now just a heading, key bindings can be added later for various 
bisect actions
-     (when (file-exists-p (expand-file-name ".git/BISECT_START" (vc-git-root 
dir)))
+     (when (file-exists-p (expand-file-name "BISECT_START" gitdir))
        (propertize  "\nBisect     : in progress" 'face 'vc-dir-status-warning))
-     (when (file-exists-p (expand-file-name ".git/rebase-apply" (vc-git-root 
dir)))
+     (when (file-exists-p (expand-file-name "rebase-apply" gitdir))
        (propertize  "\nRebase     : in progress" 'face 'vc-dir-status-warning))
      (if stash-list
          (concat
@@ -1286,8 +1304,7 @@ This prompts for a branch to merge from."
          (completing-read "Merge from branch: "
                           (if (or (member "FETCH_HEAD" branches)
                                   (not (file-readable-p
-                                        (expand-file-name ".git/FETCH_HEAD"
-                                                          root))))
+                                         (vc-git--git-path "FETCH_HEAD"))))
                               branches
                             (cons "FETCH_HEAD" branches))
                           nil t)))
@@ -1332,8 +1349,7 @@ This prompts for a branch to merge from."
       (unless (or
                (not (eq vc-git-resolve-conflicts 'unstage-maybe))
                ;; Doing a merge, so bug#20292 doesn't apply.
-               (file-exists-p (expand-file-name ".git/MERGE_HEAD"
-                                                (vc-git-root 
buffer-file-name)))
+               (file-exists-p (vc-git--git-path "MERGE_HEAD"))
                (vc-git-conflicted-files (vc-git-root buffer-file-name)))
         (vc-git-command nil 0 nil "reset"))
       (vc-resynch-buffer buffer-file-name t t)