[roll] Fix the command in the commit message

The CL https://crrev.com/c/chromium/tools/depot_tools/+/2031104 used
the full hash when calling "git log" to fix the roll on some bot. It
however resulted in the full hash visible in the commit message.

Fix the command included in the commit message while still using the
full hash in the command invoked.

Bug: none
Change-Id: I454e600fc34e554c1186ae9488ea4b0f7e7df310
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2031105
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>

roll_dep.py

@@ -127,6 +127,7 @@ def generate_commit_message(
     log_section = log_url + '\n\n'
   log_section += '$ %s ' % ' '.join(cmd)
   log_section += '--format=\'%ad %ae %s\'\n'
+  log_section = log_section.replace(commit_range, commit_range_for_header)
   # It is important that --no-log continues to work, as it is used by
   # internal -> external rollers. Please do not remove or break it.
   if not no_log and should_show_log(upstream_url):