bug#38044: 27.0.50; There should be an easier way to look at a specific vc commit

[Juri Linkov]

>> Then no dwim command is needed.  We'll just add vc-log-revision and done.
>> The user will decide whether to use vc-log-search to search in commit
>> messages, or vc-log-revision to show the log message of one commit.
>
> I'm fine with having two commands. Having a '-dwim-' one could save on key
> bindings, but we don't have one for vc-log-search anyway.

Ok, here is a new command vc-log-revision:

diff --git a/lisp/vc/vc-git.el b/lisp/vc/vc-git.el
index 5ab8e7ec53..f379c3d890 100644
--- a/lisp/vc/vc-git.el
+++ b/lisp/vc/vc-git.el
@@ -1189,7 +1189,7 @@ vc-git-log-incoming
                        "@{upstream}"
                      remote-location))))
 
-(defun vc-git-log-search (buffer pattern)
+(defun vc-git-log-search (buffer pattern &optional limit)
   "Search the log of changes for PATTERN and output results into BUFFER.
 
 PATTERN is a basic regular expression by default in Git.
@@ -1197,8 +1197,10 @@ vc-git-log-search
 Display all entries that match log messages in long format.
 With a prefix argument, ask for a command to run that will output
 log entries."
-  (let ((args `("log" "--no-color" "-i"
-                ,(format "--grep=%s" (or pattern "")))))
+  (let ((args (if limit
+                  `("log" "--no-color" "-n" "1" ,(or pattern ""))
+                `("log" "--no-color" "-i"
+                  ,(format "--grep=%s" (or pattern ""))))))
     (when current-prefix-arg
       (setq args (cdr (split-string
                       (read-shell-command
diff --git a/lisp/vc/vc.el b/lisp/vc/vc.el
index 0d29c80d02..92faa59502 100644
--- a/lisp/vc/vc.el
+++ b/lisp/vc/vc.el
@@ -2542,6 +2542,16 @@ vc-log-outgoing
     (vc-incoming-outgoing-internal backend (or remote-location "")
                                    "*vc-outgoing*" 'log-outgoing)))
 
+(defun vc-log-search-internal (backend buffer-name type pattern &optional 
limit)
+  (vc-log-internal-common
+   backend buffer-name nil type
+   (lambda (bk buf type-arg _files)
+     (vc-call-backend bk type-arg buf pattern limit))
+   (lambda (_bk _files-arg _ret) nil)
+   nil ;; Don't move point.
+   (lambda (_ignore-auto _noconfirm)
+     (vc-log-search-internal backend pattern buffer-name type))))
+
 ;;;###autoload
 (defun vc-log-search (pattern)
   "Search the log of changes for PATTERN.
@@ -2558,8 +2568,25 @@ vc-log-search
   (let ((backend (vc-deduce-backend)))
     (unless backend
       (error "Buffer is not version controlled"))
-    (vc-incoming-outgoing-internal backend pattern
-                                   "*vc-search-log*" 'log-search)))
+    (vc-log-search-internal backend "*vc-search-log*" 'log-search pattern)))
+
+;;;###autoload
+(defun vc-log-revision (revision)
+  "Search the log of changes for REVISION.
+Display the REVISION log entry in long format."
+  (interactive (list (unless current-prefix-arg
+                       (let ((default (thing-at-point 'word)))
+                         (vc-read-revision
+                          (if default
+                              (format "Revision to log (default %s): " default)
+                            "Revision to log: ")
+                          nil nil default)))))
+  (when (equal revision "")
+    (error "No revision specified"))
+  (let ((backend (vc-deduce-backend)))
+    (unless backend
+      (error "Buffer is not version controlled"))
+    (vc-log-search-internal backend "*vc-search-log*" 'log-search revision 1)))
 
 ;;;###autoload
 (defun vc-log-mergebase (_files rev1 rev2)