hook/commit-msg: Fix code review issues

Make sure the Story-Id tag handling is case-insensitive.

Story-Id: SF-15
Change-Id: 4214edc0eb
Merge branch 'develop' of github.com:salsita/salsaflow into develop
hooks/commit-msg: Fix diff separator handling

We were dropping comments before actually checking for the separator, so the
separator itself was just silently dropped as yet another comment.

Change-Id: ec0cc20335
Story-Id: SF-64
wip [ci skip]

Change-Id: bb5c8504dc