New command line option `--orig` to rename conflicting files

Hello!

Thank you for stow -- I'm enjoying it a lot. It has become the first tool that I install on a new machine after git. Also, I hope github is an OK channel for sending feature requests.

Here's my request: It'd be nice to have a new command line option --orig (or similar) to make backups of conflicting files in the target directory instead of failing on conflict. For example:

• hosts => hosts.orig
• ntp.conf => ntp.conf.orig
• .bashrc => .bashrc.orig

I often use stow to link files from a git repo into $HOME or /etc, and Linux distributions ship with default configuration files in these locations that stow will trip over. The --adopt option does not solve my problem because I don't want to copy the OS default configs into my git repo - I want to do the opposite and overwrite the OS default configs (but keep backups of them).

Leaving each backup file in the same directory as the original and using a constant backup extension (.orig) has the nice effect that one can do e.g. find /etc -name "*.orig" to find all overwritten configs. Likewise, it's fairly easy to run diff to see changes from the OS defaults.

Here's a demonstration of what currently happens:

$ mkdir demo
$ mkdir -p demo/stow/test
$ touch demo/foo demo/stow/test/foo
$ tree demo --charset ascii
demo
|-- foo
`-- stow
    `-- test
        `-- foo

2 directories, 2 files
$ (cd demo/stow && stow test)
WARNING! stowing test would cause conflicts:
  * existing target is neither a link nor a directory: foo
All operations aborted.

This is what I would like to have:

$ (cd demo/stow && stow --orig -vv test)
...
RENAME: foo => foo.orig
LINK: foo => stow/test/foo
...
$ tree demo --charset ascii
demo
|-- foo -> stow/test/foo
|-- foo.orig
`-- stow
    `-- test
        `-- foo

2 directories, 3 files

Here's a succint description of the behavior that --orig would have, covering edge cases:

• IF dst already exists THEN
  • IF dst.orig already exists THEN give up and stop with an error
  • ELSE rename dst to dst.orig(even if dst is a symlink, a directory, etc.)
    • IF the rename fails due to permissions etc. THEN give up and stop with an error

The option could also be named --backup or similar, but I personally like --orig because it's short and mnemonic (it reminds the user that the backup filename will have the extension .orig, which is also a de facto standard extension for such files).

Would you accept a feature like this into stow?

Kind regards, Lassi