the commits in the range like linkgit:git-submodule[1] `summary` does.
Omitting the `--submodule` option or specifying `--submodule=short`,
uses the 'short' format. This format just shows the names of the commits
- at the beginning and end of the range.
+ at the beginning and end of the range. Can be tweaked via the
+ `diff.submodule` configuration variable.
--color[=<when>]::
Show colored diff.