Use commit author info instead of committer info [CH-1282]

[ghengeveld]

This updates the log format to yield the author info, which is more correct for merge commits.

[linear]

CH-1282 Record commit author info

Merge commits created by GitHub have committerName: "GitHub" and committerEmail: "noreply@github.com" which is quite useless. These originate from the --format we pass when pulling up commit info in the CLI. For example:

git --no-pager log -n 1 --format="%H ## %ct ## %ce ## %cn"
55df0c1b10d868924362b89f467502d6e47dc641 ## 1639695874 ## noreply@github.com ## GitHub

Compare that to this slightly different format:

git --no-pager log -n 1 --format="%H ## %at ## %ae ## %an"
55df0c1b10d868924362b89f467502d6e47dc641 ## 1639695874 ## john@chromatic.com ## John Hobbs

We could either change our format to use %at %ae and %an, or extend the format to include these as separate fields and record them separately as authoredAt, authorName and authorEmail. In that case we could use and parse this format:

git --no-pager log -n 1 --format="%H %at%n%cn <%ce>%n%an <%ae>"
55df0c1b10d868924362b89f467502d6e47dc641 1639695874
GitHub <noreply@github.com>
John Hobbs <john@chromatic.com>

[tmeasday]

LGTM