--directory option for borg create and extract

[gleb]

man tar:

     -C, --directory DIR
           change to directory DIR

man tarsnap:

     -C directory
             (c and x modes only) In c mode, this changes the directory before
             adding the following files.  In x mode, change directories after
             opening the archive but before extracting entries from the ar‐
             chive.

Would be nice to have this.

[ThomasWaldmann]

I never got the point of these. Why not just cd before invoking tar/tarsnap/borg?

[gleb]

Personally I use it occasionally in scripts, for atomicity (in case cd fails) and lack of side effects (no need to cd back). tar -C /home is equivalent to something like cd /home && { tar ; cd - }

But I just looked at the docs https://www.gnu.org/software/tar/manual/html_node/directory.html and apparently it is meant for something else - you can use -C multiple times within tar arguments and pretty much write a program inside tar. Who knew.

And now that I know, I'd say implementing this is best avoided for now. Too complicated for not enough gain.

[edgewood]

On Sun, Oct 30, 2016 at 10:15:21PM -0700, gleb wrote:

Personally I use it occasionally in scripts, for atomicity (in case cd fails) and lack of side effects (no need to cd back). tar -C /home is equivalent to something like cd /home && { tar ; cd - }

Note that starting a subshell will isolate environmental changes
(including working directory) to the subshell. No need to change things
back to the way they were, just copy the current environment, change the
copy, and throw the copy away when you're done.

For example:
( cd /home && borg create ... )

Ed Blackman

[gleb]

Good point, thanks!

[MarkMielke]

I wanted the ability to treat the source directory as irrelevant. This seems to be possible with:

cd /source/directory && borg create ARCHIVE "."

Using --directory or similar would formalize this capability and make it easier to access.

I haven't yet found documentation approving of the "." as a valid use case, so I'm partially concerned that I'm doing something wrong, and this lead me to this issue.

[ThomasWaldmann]

There is nothing wrong with . (just make sure you are really where you want to be).

[alexconstsh]

@ThomasWaldmann Is there anything missing from @unilynx's code mentioned in #5604?

[ThomasWaldmann]

@alexconstsh yeah:

• it should not be in a "docker issue" (but rather here)
• there should be a PR request to discuss it
• docs
• tests

[alexconstsh]

@unilynx hi. Are you willing to continue work on this feature? If not, I would like to take your code under Borg's license and work from there.

[unilynx]

@unilynx hi. Are you willing to continue work on this feature? If not, I would like to take your code under Borg's license and work from there.

By all means, go ahead! I still haven't gotten around to it and it would be nice to have.

[ThomasWaldmann]

See also #4685 for more problems.