bug#19045: 25.0.50; [PATCH] vc-git-print-log use --follow

[Juri Linkov <juri@linkov.net>]

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Too bad that a new useful customizable variable
vc-git-print-log-follow is not mentioned in NEWS.26.

It works quite well, but only with the following fix
that puts more restrictions - it checks not only
for a directory, but also if it is a single file.

The whole patch is intended for the emacs-26 branch:


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diff --git a/etc/NEWS b/etc/NEWS
index 5b3e445..6aa4b2d 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1169,6 +1169,9 @@ branch-related commands on a keymap bound to 'B'.
 *** 'vc-region-history' is now bound to 'C-x v h', replacing the older
 'vc-insert-headers' binding.
 
+*** New user option 'vc-git-print-log-follow' follow renames in Git logs
+for a single file.
+
 ** CC mode
 
 ---
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 3bf837c..9b54b88 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -994,7 +994,7 @@ This prompts for a branch to merge from."
 (autoload 'vc-setup-buffer "vc-dispatcher")
 
 (defcustom vc-git-print-log-follow nil
-  "If true, follow renames in Git logs for files."
+  "If true, follow renames in Git logs for a single file."
   :type 'boolean
   :version "26.1")
 
@@ -1019,8 +1019,9 @@ If LIMIT is non-nil, show no more than this many entries."
 	       (append
 		'("log" "--no-color")
                 (when (and vc-git-print-log-follow
-                           (not (cl-some #'file-directory-p files)))
-                  ;; "--follow" on directories is broken
+                           (null (cdr files))
+                           (not (file-directory-p (car files))))
+                  ;; "--follow" on directories or multiple files is broken
                   ;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=8756
                   ;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=16422
                   (list "--follow"))