### Please describe the problem.

previously reported and partially addressed in [here](https://git-annex.branchable.com/bugs/impossible_to_perform___34__read-only__34___git_annex_info_without_write_permissions/)


### What steps will reproduce the problem?

try any presumably read-only annex operation (whereis, wanted, etc) on a repository where you have no write permissions.

` -c annex.merge-annex-branches=false ` configuration switch was introduced to allow for running `whereis` in "read-only" mode.  But it requires user knowhow and good memory.
It is also inconsistent with how `git` behaves in that it doesn't require any extra option and just handles it automagically/gracefully.

If git-annex could automagically switch to such mode when encountering read-only repository, may be announcing that on stderr, that would make life so much easier.

Also it seems that some commands are not even fully support it:

```
[d31548v@discovery7 1076_spacetop]$ git annex wanted here
git-annex: /dartfs/rc/lab/D/DBIC/DBIC/archive/BIDS/Wager/Wager/1076_spacetop/.git/annex: openTempFile template locktmp: permission denied (Permission denied)
git-annex: /dartfs/rc/lab/D/DBIC/DBIC/archive/BIDS/Wager/Wager/1076_spacetop/.git/annex: openTempFile template locktmp: permission denied (Permission denied)
[d31548v@discovery7 1076_spacetop]$ git  -c annex.merge-annex-branches=false annex wanted here

git-annex: /dartfs/rc/lab/D/DBIC/DBIC/archive/BIDS/Wager/Wager/1076_spacetop/.git/annex: openTempFile template locktmp: permission denied (Permission denied)
[d31548v@discovery7 1076_spacetop]$ git annex version | head -n 1
git-annex version: 8.20211117+git14-ge1f38b9dd-1~ndall+1
```

[[!meta author=yoh]]
[[!tag projects/datalad]]

> [[done]] --[[Joey]]
