gitlint: ignore body lines that are footnotes

Ignore lines that start like `[1]: ` or `[2] ` such that we can have
long text like URLs in the commits without triggering other gitlint body
rules.

Copied from the same changes already made in samba-container
(PR samba-in-kubernetes/samba-container#150).

Signed-off-by: John Mulligan <jmulligan@redhat.com>

Author: phlogistonjohn

.gitlint

@@ -30,6 +30,9 @@ ignore-merge-commits=true
 # Enable debug mode (prints more output). Disabled by default.
 # debug=true
 
+# Enable search regex and remove warning message.
+regex-style-search=true
+
 # Enable community contributed rules
 # See http://jorisroovers.github.io/gitlint/contrib_rules for details
 contrib=contrib-body-requires-signed-off-by
@@ -106,11 +109,16 @@ regex=^.{2,32}: .*
 # Use 'all' to ignore all rules
 # ignore=T1,body-min-length
 
-# [ignore-body-lines]
+[ignore-body-lines]
 # Ignore certain lines in a commit body that match a regex.
 # E.g. Ignore all lines that start with 'Co-Authored-By'
 # regex=^Co-Authored-By
 
+# ignore lines that are "footnotes", that start like `[1]: ` or `[2]: ` and so on
+# this will make it easy to put long urls in commit messages without
+# triggering gitlint body rules
+regex=^\[[0-9]+\]:? +
+
 # This is a contrib rule - a community contributed rule. These are disabled by default.
 # You need to explicitly enable them one-by-one by adding them to the "contrib" option
 # under [general] section above.