Merge branch 'et/pretty-format-c-auto' into maint

The commands in `git log` family take %C(auto) in a custom format string. This unconditionally turned the color on, ignoring --no-color or with --color=auto when the output is not connected to a tty; this was corrected to make the format truly behave as "auto". * et/pretty-format-c-auto: format_commit_message: honor `color=auto` for `%C(auto)`