Add option to have it be completely silent when committing

README.org

@@ -109,3 +109,8 @@
   - =gac-commit-additional-flag= ::
     A string that can be used to add additional command line flags to the ~git
     commit~ command.
+
+  - =gac-silent-message-p= ::
+    A boolean value indicating whether to display the commit summary message,
+    which is usually displayed in the minibuffer. The default is ~nil~, meaning
+    that the summary would be displayed on every commit.

git-auto-commit-mode.el

@@ -81,6 +81,12 @@ If non-nil a git push will be executed after each commit."
     :group 'git-auto-commit-mode
     :type 'string)
 
+(defcustom gac-silent-message-p nil
+    "Should git output be output to the message area?"
+    :tag "Quiet message output"
+    :group 'git-auto-commit-mode
+    :type 'boolean)
+
 
 (defcustom gac-debounce-interval nil
   "Debounce automatic commits to avoid hammering Git.
@@ -172,7 +178,9 @@ Default to FILENAME."
                     (file-name-nondirectory buffer-file)))
          (commit-msg (gac--commit-msg buffer-file))
          (default-directory (file-name-directory buffer-file)))
-    (shell-command
+    (funcall (if gac-silent-message-p
+                 #'call-process-shell-command
+                 #'shell-command)
      (concat "git add " gac-add-additional-flag " " (shell-quote-argument filename)
              gac-shell-and
              "git commit -m " (shell-quote-argument commit-msg)