The current signature of `git_worktree_prune` accepts a flags field to alter its behavior. This is not as flexible as we'd like it to be when we want to enable passing additional options in the future. As the function has not been part of any release yet, we are still free to alter its current signature. This commit does so by using our usual pattern of an options structure, which is easily extendable without breaking the API.
When creating a new worktree, we do have a potential race with us creating the worktree and another process trying to delete the same worktree as it is being created. As such, the upstream git project has introduced a flag `git worktree add --locked`, which will cause the newly created worktree to be locked immediately after its creation. This mitigates the race condition. We want to be able to mirror the same behavior. As such, a new flag `locked` is added to the options structure of `git_worktree_add` which allows the user to enable this behavior.
The `git_worktree_add` function currently accepts only a path and name for the new work tree. As we may want to expand these parameters in future versions without adding additional parameters to the function for every option, this commit introduces our typical pattern of an options struct. Right now, this structure is still empty, which will change with the next commit.
Whenever we rename a branch, we update the repository's symbolic HEAD reference if it currently points to the branch that is to be renamed. But with the introduction of worktrees, we also have to iterate over all HEADs of linked worktrees to adjust them. Do so.
It is possible to specify submodule URLs relative to the repository location. E.g. having a submodule with URL "../submodule" will look for the submodule at "repo/../submodule". With the introduction of worktrees, though, we cannot simply resolve the URL relative to the repository location itself. If the repository for which a URL is to be resolved is a working tree, we have to resolve the URL relative to the parent's repository path. Otherwise, the URL would change depending on where the working tree is located. Fix this by special-casing when we have a working tree while getting the URL base.
References for a repository are usually created inside of its gitdir. When using worktrees, though, these references are not to be created inside the worktree gitdir, but instead inside the gitdir of its parent repository, which is the commondir. Like this, branches will still be available after the worktree itself has been deleted. The filesystem refdb currently still creates new references inside of the gitdir. Fix this and have it create references in commondir.
The three link files "worktree/.git", ".git/worktrees/<name>/commondir" and ".git/worktrees/<name>/gitdir" should always contain absolute and resolved paths. Adjust the logic creating new worktrees to first use `git_path_prettify_dir` before writing out these files, so that paths are resolved first.
The working tree's parent path should not point to the parent's gitdir, but to the parent's working directory. Pointing to the gitdir would not make any sense, as the parent's working directory is actually equal to both repository's common directory. Fix the issue.
While we already provide functionality to look up a worktree from a repository, we cannot do so the other way round. That is given a repository, we want to look up its worktree if it actually exists. Getting the worktree of a repository is useful when we want to get certain meta information like the parent's location, getting the locked status, etc.