Win/BF: don't invoke 'git-annex' but 'git annex'

[adswa]

On a Windows machine, while git-annex and git annex invocations work fine from an Anaconda prompt, a "git-annex" command invoked via run_annex_command fails to find the git-annex executable.
When using 'git annex', though, commands seem to work just fine. This change fixes #4892. I lack an in-depth understanding of why that is, yet, but I also figured that this change doesn't do harm to anything else.

[codecov]

Codecov Report

Merging #5001 into maint will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##            maint    #5001   +/-   ##
=======================================
  Coverage   89.91%   89.91%           
=======================================
  Files         292      292           
  Lines       40736    40736           
=======================================
  Hits        36629    36629           
  Misses       4107     4107           

Impacted Files	Coverage Δ
datalad/customremotes/base.py	87.45% <ø> (ø)
datalad/customremotes/archives.py	91.95% <100.00%> (ø)
datalad/support/annexrepo.py	86.84% <100.00%> (ø)
datalad/tests/test_cmd.py	97.48% <100.00%> (ø)

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[mih]

I agree, this should do not harm. But I also lack insight on why it would make a difference.

[kyleam]

As you and @mih say, I don't see how this would be problematic, and there are places in the code (including a couple of non-test spots) that already use the separated variant that this PR switches to.

A few comments:

• Grepping for ["']git-annex["'] is noisy, but I see at least a few other instances that might trigger the same issue (e.g., a ["git-annex", "get", ...] in datalad/customremotes/archives.py).

• Since it's not obvious what's going on here, it'd be nice to add a code comment in _run_annex_command that mentions the importantance of the separated form.

• I think this could go to maint.

[adswa]

Thanks much for your comments, Kyle! I think I have applied them, and I hope I caught all git-annex command calls.I rebased onto maint.

[kyleam]

Thanks for the updates.

I'm going to restart the failing macOS build to see if that failure goes away. (If it does, I'll open a separate issue for the apparently intermittent failure.)

https://github.com/datalad/datalad/pull/5001/checks?check_run_id=1237765992

edit: restarted build passed

https://github.com/datalad/datalad/pull/5001/checks?check_run_id=1242140615

[kyleam]

(If it does, I'll open a separate issue for the apparently intermittent failure.)

Just to follow up on this: I was about to do that now, but I don't recall seeing it elsewhere, and it looks to be an internal git-annex locking issue, so I'll wait to see if it pops up again before opening an issue that nobody will be able to act on.