This fixes the failure of `git cmd --help` where `cmd` is some
git-branchless alias.
The error is due to a quirk of git: when supplied with the long form
`--help` flag, the git binary eats the flag and instead look for man
page of `cmd`. This errors out unless the man page for `cmd` is properly
installed. In the case of `git-branchless`, this can be achieved with
the command `git-branchless install-man-pages`, as implemented in this
patch.
We do not use a "plugin system" for Git addons anymore, and therefore this
directory is no longer useful. Indeed that directory is way more confusing,
given that it includes more than mere Git addons, going from Bitbucket server
command-line tools to complete rewrites of Git in exotic programming languages.
Also, without this directory, the mental load of decision-making reduces a lot.
When anyone is interested in including a new git-related tool, just put it into
pkgs/applications/version-management, without apologies.
