René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"git_worktree_add fails on master branch with already checked out","articleBody":"Other branches work all OK just seems to be the master that fails.  Note that the repo is bare just in case that has any effect.\r\n \r\n### Reproduction steps\r\n```\r\ngit clone --bare url\r\n```\r\n```\r\n    git_reference_lookup(ref, Handle, 'refs/heads/master')\r\n    git_worktree_add_init_options(@opts, GIT_WORKTREE_ADD_OPTIONS_VERSION);\r\n    opts.ref := ref;\r\n    r := git_worktree_add(wt, Handle, 'worktreename', '/some/path', @opts)\r\n```\r\n### Expected behavior\r\nr = 0 (Success)\r\n\r\n### Actual behavior\r\nr = -4 (Fail)\r\nError message = \"reference is already checked out\"\r\n\r\n### Version of libgit2 (release number or SHA1)\r\n0.28\r\n\r\n### Operating system(s) tested\r\nWindows\r\n\r\n### Additional Information\r\nAfter the failure partial work tree structure is left behind which maybe should have been cleaned up or maybe the validity checks should happen before any structure gets created - which may or may not be possible.  \r\n\r\nAnyway if I clear out the invalid worktree structure that was left behind and run\r\n```\r\ngit worktree add --checkout /some/path master\r\n```\r\nit works just fine so we know that the master was not checked out anywhere else\r\n\r\n","author":{"url":"https://github.com/mjnz","@type":"Person","name":"mjnz"},"datePublished":"2019-02-13T00:32:09.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/4977/libgit2/issues/4977"}