Improve docs on rebaseline git config user name/email override.

scripts/slave/recipes/infra/rebaseline_o_matic.py

Index: scripts/slave/recipes/infra/rebaseline_o_matic.py
diff --git a/scripts/slave/recipes/infra/rebaseline_o_matic.py b/scripts/slave/recipes/infra/rebaseline_o_matic.py
index c9683fa1d73dbe19eaaf68a5a8102e260c552e40..bbf11b03e68955092b9c15b04379fdd1a09384cd 100644
--- a/scripts/slave/recipes/infra/rebaseline_o_matic.py
+++ b/scripts/slave/recipes/infra/rebaseline_o_matic.py
@@ -31,6 +31,17 @@ def RunSteps(api):
   cwd = api.path['checkout'].join('third_party', 'WebKit')
 
   # Changes should be committed and landed as the rebaseline bot role account.
+  # The base chromium repo setup configures chrome-bot@ as the author/committer.
+  # We could attempt use of command-line arguments to git commands to specify
+  # the rebaseline bot name/email, but in fact this is insufficient to override
+  # due to precedence. Environment variables would likely work per the man page
+  # for git-commit-tree, but would require changes through both the auto-
+  # rebaseline script and 'git cl land', with this bot as the only intended
+  # customer.
+  #
+  # Given all tradeoffs, setting the chromium repo's user name/email to the
+  # intended rebaseline bot parameters in a persistent manner is deemed a
+  # reasonable alternate approach.
   api.git('config', 'user.name', 'Rebaseline Bot')
   api.git('config', 'user.email', 'blink-rebaseline-bot@chromium.org')