Fix 'diff-goto-source' when buffer is narrowed (Bug#21262)

* lisp/vc/diff-mode.el (diff-find-file-name): Save the current
narrowing, and widen the buffer before searching for the name of the
file corresponding to the diff.

With thanks to Noam Postavsky.

1 files changed, 47 insertions, 45 deletions

diff --git a/lisp/vc/diff-mode.el b/lisp/vc/diff-mode.el
index aa8d77882ec..1d4af54db93 100644
--- a/lisp/vc/diff-mode.el
+++ b/lisp/vc/diff-mode.el
@@ -875,51 +875,53 @@ PREFIX is only used internally: don't use it."
     (set (make-local-variable 'diff-remembered-defdir) default-directory)
     (set (make-local-variable 'diff-remembered-files-alist) nil))
   (save-excursion
-    (unless (looking-at diff-file-header-re)
-      (or (ignore-errors (diff-beginning-of-file))
-          (re-search-forward diff-file-header-re nil t)))
-    (let ((fs (diff-hunk-file-names old)))
-      (if prefix (setq fs (mapcar (lambda (f) (concat prefix f)) fs)))
-      (or
-       ;; use any previously used preference
-       (cdr (assoc fs diff-remembered-files-alist))
-       ;; try to be clever and use previous choices as an inspiration
-       (cl-dolist (rf diff-remembered-files-alist)
-         (let ((newfile (diff-merge-strings (caar rf) (car fs) (cdr rf))))
-           (if (and newfile (file-exists-p newfile)) (cl-return newfile))))
-       ;; look for each file in turn.  If none found, try again but
-       ;; ignoring the first level of directory, ...
-       (cl-do* ((files fs (delq nil (mapcar 'diff-filename-drop-dir files)))
-                (file nil nil))
-           ((or (null files)
-                (setq file (cl-do* ((files files (cdr files))
-                                    (file (car files) (car files)))
-                               ;; Use file-regular-p to avoid
-                               ;; /dev/null, directories, etc.
-                               ((or (null file) (file-regular-p file))
-                                file))))
-            file))
-       ;; <foo>.rej patches implicitly apply to <foo>
-       (and (string-match "\\.rej\\'" (or buffer-file-name ""))
-            (let ((file (substring buffer-file-name 0 (match-beginning 0))))
-              (when (file-exists-p file) file)))
-       ;; If we haven't found the file, maybe it's because we haven't paid
-       ;; attention to the PCL-CVS hint.
-       (and (not prefix)
-            (boundp 'cvs-pcl-cvs-dirchange-re)
-            (save-excursion
-              (re-search-backward cvs-pcl-cvs-dirchange-re nil t))
-            (diff-find-file-name old noprompt (match-string 1)))
-       ;; if all else fails, ask the user
-       (unless noprompt
-         (let ((file (expand-file-name (or (car fs) ""))))
-           (setq file
-                 (read-file-name (format "Use file %s: " file)
-                                 (file-name-directory file) file t
-                                 (file-name-nondirectory file)))
-           (set (make-local-variable 'diff-remembered-files-alist)
-                (cons (cons fs file) diff-remembered-files-alist))
-           file))))))
+    (save-restriction
+      (widen)
+      (unless (looking-at diff-file-header-re)
+        (or (ignore-errors (diff-beginning-of-file))
+            (re-search-forward diff-file-header-re nil t)))
+      (let ((fs (diff-hunk-file-names old)))
+        (if prefix (setq fs (mapcar (lambda (f) (concat prefix f)) fs)))
+        (or
+         ;; use any previously used preference
+         (cdr (assoc fs diff-remembered-files-alist))
+         ;; try to be clever and use previous choices as an inspiration
+         (cl-dolist (rf diff-remembered-files-alist)
+           (let ((newfile (diff-merge-strings (caar rf) (car fs) (cdr rf))))
+             (if (and newfile (file-exists-p newfile)) (cl-return newfile))))
+         ;; look for each file in turn.  If none found, try again but
+         ;; ignoring the first level of directory, ...
+         (cl-do* ((files fs (delq nil (mapcar 'diff-filename-drop-dir files)))
+                  (file nil nil))
+             ((or (null files)
+                  (setq file (cl-do* ((files files (cdr files))
+                                      (file (car files) (car files)))
+                                 ;; Use file-regular-p to avoid
+                                 ;; /dev/null, directories, etc.
+                                 ((or (null file) (file-regular-p file))
+                                  file))))
+              file))
+         ;; <foo>.rej patches implicitly apply to <foo>
+         (and (string-match "\\.rej\\'" (or buffer-file-name ""))
+              (let ((file (substring buffer-file-name 0 (match-beginning 0))))
+                (when (file-exists-p file) file)))
+         ;; If we haven't found the file, maybe it's because we haven't paid
+         ;; attention to the PCL-CVS hint.
+         (and (not prefix)
+              (boundp 'cvs-pcl-cvs-dirchange-re)
+              (save-excursion
+                (re-search-backward cvs-pcl-cvs-dirchange-re nil t))
+              (diff-find-file-name old noprompt (match-string 1)))
+         ;; if all else fails, ask the user
+         (unless noprompt
+           (let ((file (expand-file-name (or (car fs) ""))))
+             (setq file
+                   (read-file-name (format "Use file %s: " file)
+                                   (file-name-directory file) file t
+                                   (file-name-nondirectory file)))
+             (set (make-local-variable 'diff-remembered-files-alist)
+                  (cons (cons fs file) diff-remembered-files-alist))
+             file)))))))
 
 
 (defun diff-ediff-patch ()