Add --dry-run option

Again this is useful for scripting. We can now test the whole chain
with:

  git publish -v --base origin/master --skip-final-edit --no-inspect-emails --dry-run

before finally hitting the big red button.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Author: stsquad

git-publish

@@ -640,6 +640,9 @@ def parse_args():
     parser.add_argument('--skip-final-edit', dest='skip_final_edit',
                         action='store_true', default=False,
                         help='Skip final edit step (useful for scripting)')
+    parser.add_argument('--dry-run', dest='dry_run',
+                        action='store_true', default=False,
+                        help='Non-interactive dry run (suitable for scripting)')
 
     return parser.parse_known_args()
 
@@ -936,9 +939,13 @@ branch.%s.pushRemote is set appropriately?  (Override with --no-check-url)''' %
 
             if (options.separate_send):
                 for patch in selected_patches:
-                    git_send_email(to, cc, [patch], suppress_cc, options.in_reply_to, options.thread)
+                    git_send_email(to, cc, [patch], suppress_cc,
+                                   options.in_reply_to,
+                                   options.thread, dry_run=options.dry_run)
             else:
-                git_send_email(to, cc, selected_patches, suppress_cc, options.in_reply_to, options.thread)
+                git_send_email(to, cc, selected_patches, suppress_cc,
+                               options.in_reply_to, options.thread,
+                               dry_run=options.dry_run)
         except (GitSendEmailError, GitHookError, InspectEmailsError):
             return 1
         except GitError as e:
@@ -950,7 +957,7 @@ branch.%s.pushRemote is set appropriately?  (Override with --no-check-url)''' %
 
         git_save_email_lists(topic, to, cc, options.override_cc)
 
-        if not options.pull_request:
+        if not options.pull_request and not options.dry_run:
             # Publishing is done, stablize the tag now
             _git_check('tag', '-f', tag_name(topic, number), tag_name_staging(topic))
             git_delete_tag(tag_name_staging(topic))