Fix the 'edit on github' link for stable versions of a projet

[magopian]

Fixes #1820

This is a naive approach, and might break things, for example for other VCS
than GitHub. Feedback welcome!

The rationale here is that the identifier of the stable build is the hash
of the tag, and not of a commit. It thus leads to a 404 when building the link
to edit on GitHub (see the comment in the original
issue).
If instead of storing the tag hash in the identifier we stored the
verbose_name of the original branch (its name), it would be used to build the
link (just the same way we use the verbose name for tags, and not commit
hashes).

[techtonik]

Is it possible to get test for that?

I am afraid I need more complete picture on how readthedocs works with tags, branches and slugs.

[magopian]

Sure, any tips on where I should put it? readthedocs/rtd_tests/tests/test_sync_versions.py maybe?

[leplatrem]

@magopian let's assume test_sync_versions.py is the right location and we move on :)

[berkerpeksag]

Yes, readthedocs/rtd_tests/tests/test_sync_versions.py is a good place to put the test. There is already a test for the update_stable_version method so some parts of it can be reused :)

[ericholscher]

I've looked at this, and it just seems to change the identifier for the stable version on creation. If we want to fix this, it will need to be back ported to all projects with a migration.

Another way to fix this is with logic on the display, when we have a stable branch, link to some other path on the repo.

[ericholscher]

The link in the footer is actually doing the correct thing (as you can see here: http://mockingjay.readthedocs.io/en/stable/) -- so we just need to fix the variable passed to the button.

[ericholscher]

Actually looks like this has been fixed, so closing this PR :)