RFC: Remove vcs_info backends cdv, svk, tla? (was: Re: [PATCH v5] vcs_info: choose backend by basedir)

[Daniel Shahaf <d.s@daniel.shahaf.name>]

Aleksandr Mezin wrote on Fri, Jun 04, 2021 at 12:14:21 +0600:
> @@ -124,10 +129,59 @@ vcs_info () {
>          vcs_comm=()
>          VCS_INFO_get_cmd
> -        VCS_INFO_detect_${vcs} && (( found = 1 )) && break
> +        if VCS_INFO_detect_${vcs}; then
> +            # Most backends already set vcs_comm[basedir] to an absolute path
> +            # with symlinks resolved:
> +            #
> +            # * Backends using VCS_INFO_bydir_detect:
> +            #   bzr, cdv, darcs, fossil, hg, mtn, p4, svn
> +            #
> +            # * cvs - custom logic, but uses :P too
> +            #
> +            # * git - $(git rev-parse --show-toplevel) resolves symlinks and
> +            #   returns an absolute path
> +            #
> +            # * for tla (GNU Arch) I can't find any online documentation or
> +            #   packages (seems to be dead)
> +            #

There's https://savannah.gnu.org/projects/gnu-arch/.  It says tla is
"decommissioned" and hasn't had a release in 16 years.  There's also
<https://www.gnu.org/software/gnu-arch/>, but it doesn't alter the
bottom line.

> +            # * svk doesn't use :P modifier and returns the path as is from
> +            #   the config file (as far as I understand)
> +            #

Does anyone still use svk?  It was a "distributed version control for
Subversion" thing (https://metacpan.org/dist/SVK), but:

- It hasn't had a release since 2010

- Its homepage redirects elsewhere

- Its repository is 404 Not Found

- I haven't seen any mention of it on svn's lists in years

- The list of features at the top of its man page seems to be mostly
  features that git-svn and hgsubversion already take care of.  "Working
  copy without .svn" _might_ be an exception, if they mean no text
  bases; but they could just mean "there's a single .${vcs} dir at the
  top directory, rather than foo/bar/.${vcs} inside every versioned
  foo/bar/ directory", in which case, that's not a selling point either
  nowadays.

>

Looking at the other backends, cdv hasn't had a release in 16 years,
either.  Every other backend seems to be active to one degree or
another.

> +            # So I'm not sure whether to modify the backends or just resolve
> +            # the path here to be sure. VCS_INFO_get_data_* usually reads
> +            # vcs_comm[basedir] too. In particular, I'm not sure if it's safe to
> +            # resolve symlinks in vcs_comm[basedir] for svk.

The cdv, svk, tla backends presumably have no remaining users; having
them at all imposes extra costs on people making «vcs_info»-wide changes;
and if we remove them, we can always recover them from history if they
turn out to have users after all.

So, shall we remove these three backends?

Cheers,

Daniel


> +            # Because most backends already do :P substitution, I expect all
> +            # the info needed to resolve the path to be cached in memory by the
> +            # OS (so it shouldn't cause performance issues).
> +            basedir_realpath="${vcs_comm[basedir]:P}"