git_repository_set_head: use tag name in reflog
Debian and Ubuntu often use schroot to build their DEB packages in a controlled environment. Depending on how schroot is configured, our tests regarding repository discovery break due to not being able to find the repositories anymore. It turns out that these errors occur when the schroot is configured to use an overlayfs on the directory structures. The reason for this failure is that we usually refrain from discovering repositories across devices. But unfortunately, overlayfs does not have consistent device identifiers for all its files but will instead use the device number of the filesystem the file stems from. So whenever we cross boundaries between the upper and lower layer of the overlay, we will fail to properly detect the repository and bail out. This commit fixes the issue by enabling cross-device discovery in our tests. While it would be preferable to have this turned off, it probably won't do much harm anyway as we set up our tests in a temporary location outside of the parent repository.
When `git_repository_set_head` is provided a remote reference, update the reflog with the tag name, like we do with a branch. This helps consumers match the semantics of `git checkout remote`.
When `git_repository_set_head` is provided a tag reference, update the reflog with the tag name, like we do with a branch. This helps consumers match the semantics of `git checkout tag`.
Provide more detailed messages when conditions pass or fail unexpectedly. In particular, this provides the error messages when a test fails with a different error code than was expected.
As of recently, we failed to correctly discover repositories at a
Win32 system root. Instead of aborting the upwards-traversal of
the file system, we were looping infinitely when traversal
started at either a Win32 drive prefix ("C:/") or a network path
("//somehost").
The issue has been fixed, so add a test to catch regressions.
When trying to find a discovery, we walk up the directory structure checking if there is a ".git" file or directory and, if so, check its validity. But in the case that we've got a ".git" file, we do not want to unconditionally assume that the file is in fact a ".git" file and treat it as such, as we would error out if it is not. Fix the issue by only treating a file as a gitlink file if it ends with "/.git". This allows users of the function to discover a repository by handing in any path contained inside of a git repository.