Fix vc-annotate-show-log-revision-at-line

* lisp/vc/vc-annotate.el (vc-annotate-show-log-revision-at-line):
Stop from being affected by 'vc-git-print-log-follow'.

* lisp/vc/vc-git.el (vc-git-print-log-follow):
Mention caveats in a comment.

2 files changed, 11 insertions, 0 deletions

diff --git a/lisp/vc/vc-annotate.el b/lisp/vc/vc-annotate.el
index 82531f742e4..45bb17749bc 100644
--- a/lisp/vc/vc-annotate.el
+++ b/lisp/vc/vc-annotate.el
@@ -545,6 +545,7 @@ Return a cons (REV . FILENAME)."
 
 (defvar log-view-vc-backend)
 (defvar log-view-vc-fileset)
+(defvar vc-git-print-log-follow)
 
 (defun vc-annotate-show-log-revision-at-line ()
   "Visit the log of the revision at line.
@@ -559,6 +560,8 @@ the file in question, search for the log entry required and move point."
 	  (message "Cannot extract revision number from the current line")
 	(let ((backend vc-annotate-backend)
 	      (log-buf (get-buffer "*vc-change-log*"))
+              ;; No need to follow renames: we specify the historical file name.
+              vc-git-print-log-follow
 	      pos)
 	  (if (and
 	       log-buf
diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 8332600c690..eca8d547a90 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1147,6 +1147,14 @@ This prompts for a branch to merge from."
 
 (autoload 'vc-setup-buffer "vc-dispatcher")
 
+;; It's a weird option due to how Git handles '--follow', and it can
+;; hide certain (usually merge) commits in the `vc-print-log' buffers.
+;;
+;; (setq vc-git-log-switches '("-m")) can fix that, but at the cost of
+;; duplicating many merge commits in the log.
+;;
+;; Long explanation here:
+;; https://stackoverflow.com/questions/46487476/git-log-follow-graph-skips-commits
 (defcustom vc-git-print-log-follow nil
   "If true, follow renames in Git logs for a single file."
   :type 'boolean