Deal with unlocked files in a robust fashion

[mih]

This is the sibling issue of datalad/datalad#1651

Here is the replay using -revolution code:

(datalad3-dev) mih@meiner /tmp % datalad rev-create /tmp/testunlock
[INFO   ] Creating a new annex repo at /tmp/testunlock 
create(ok): /tmp/testunlock (dataset)
(datalad3-dev) mih@meiner /tmp % cd testunlock
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % echo 123 > 123
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save
add(ok): 123 (file)
save(ok): .
action summary:
  add (ok: 1)
  save (ok: 1)
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad unlock 123
unlock(ok): /tmp/testunlock/123 (file)
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save
add(ok): 123 (file)
action summary:
  add (ok: 1)
  save (notneeded: 1)
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad unlock 123
unlock(ok): /tmp/testunlock/123 (file)
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % cat .gitattributes

* annex.backend=MD5E
**/.git* annex.largefiles=nothing%                                                              (datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % printf '\n* annex.largefiles=(not(mimetype=text/*' >> .gitattributes  
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % cat .gitattributes

* annex.backend=MD5E
**/.git* annex.largefiles=nothing
* annex.largefiles=(not(mimetype=text/*%                                                        (datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad save -m 'all text files go to git' .gitattributes
save(ok): /tmp/testunlock (dataset)
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % git st
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

        typechange: 123

no changes added to commit (use "git add" and/or "git commit -a")
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad unlock 123
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save 123
add(ok): 123 (file)
add(ok): 123 (file)
Failed to run ['git', '-c', 'receive.autogc=0', '-c', 'gc.auto=0', 'commit', '-m', '[DATALAD] Recorded changes', '--', '123'] under '/tmp/testunlock'. Exit code=1. out= err=git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.

git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.
(datalad3-dev) 1 mih@meiner /tmp/testunlock (git)-[master] % git st
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        typechange: 123

(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % git reset HEAD 123
Unstaged changes after reset:
T       123
(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save
add(ok): 123 (file)
add(ok): 123 (file)
Failed to run ['git', '-c', 'receive.autogc=0', '-c', 'gc.auto=0', 'commit', '-m', '[DATALAD] Recorded changes', '--', '123'] under '/tmp/testunlock'. Exit code=1. out= err=git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.

git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.
(datalad3-dev) 1 mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save 123
Failed to run ['git', '-c', 'receive.autogc=0', '-c', 'gc.auto=0', 'commit', '-m', '[DATALAD] Recorded changes', '--', '123'] under '/tmp/testunlock'. Exit code=1. out= err=git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.

git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.
(datalad3-dev) 1 mih@meiner /tmp/testunlock (git)-[master] % git st
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        typechange: 123

(datalad3-dev) mih@meiner /tmp/testunlock (git)-[master] % datalad rev-save
Failed to run ['git', '-c', 'receive.autogc=0', '-c', 'gc.auto=0', 'commit', '-m', '[DATALAD] Recorded changes', '--', '123'] under '/tmp/testunlock'. Exit code=1. out= err=git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.

git-annex: Cannot make a partial commit with unlocked annexed files. You should `git annex add` the files you want to commit, and then run git commit.