Redmine

git actually guides the users to use the first line of the log message as a subject, like in email.

DISCUSSION
       Though not required, it's a good idea to begin the commit message with
       a single short (less than 50 character) line summarizing the change,
       followed by a blank line and then a more thorough description. Tools
       that turn commits into email, for example, use the first line on the
       Subject: line and the rest of the commit in the body.

I think it's generally a good idea to show only the one line summary of the revision when there are lot of them to list, since I can get better view of the whole, than each commits having different heights from different lines of commit logs.

For instance, github commits page shows only the first line, and have a button where you could expand to the whole message. I personally wouldn't mind if there is no expand button, since I could click the the revision and read it inside.