Re: [PATCH 00/30] Add directory rename detection to git
From: "Elijah Newren": Friday, November 10, 2017 11:26 PM On Fri, Nov 10, 2017 at 2:27 PM, Philip Oakley wrote: From: "Elijah Newren" In this patchset, I introduce directory rename detection to merge-recursive, predominantly so that when files are added to directories on one side of history and those directories are renamed on the other side of history, the files will end up in the proper location after a merge or cherry-pick. However, this isn't limited to that simplistic case. More interesting possibilities exist, such as: * a file being renamed into a directory which is renamed on the other side of history, causing the need for a transitive rename. How does this cope with the case insensitive case preserving file systems on Mac and Windows, esp when core.ignorecase is true. If it's a bigger problem that the series already covers, would the likely changes be reasonably localised? This came up recently on GfW for `git checkout` of a branch where the case changed ("Test" <-> "test"), but git didn't notice that it needed to rename the directories on such an file system. https://github.com/git-for-windows/git/issues/1333 I wasn't aware there were problems with git on case insensitive case preserving filesystems; fixing them wasn't something I had in mind when writing this series. I was mainly ensuring awareness of the potential issue, as it's not easy to solve. However, the particular bug you mention is actually completely orthogonal to this series; it talks about git-checkout without the -m/--merge option, which doesn't touch any code path I modified in my series, so my series can't really fix or worsen that particular issue. That's good. But, if there are further issues with such filesystems that also affect merges/cherry-picks/rebases, then I don't think my series will either help or hurt there either. The recursive merge machinery already has remove_file() and update_file() wrappers that it uses whenever it needs to remove/add/update a file in the working directory and/or index, and I have simply continued using those, so the number of places you'd need to modify to fix issues would remain just as localized as before. It's when the working directory path/filename has a case change that goes undetected (one way or another) that can cause issues. I think that part of the problem (after awareness) is not having a cannonical expectation of which way is 'right', and what options there may be. E,g. if a project is wholly on a case insensitive system then the filenames in the worktree never matter, but aligning the path/filenames in the repository would still be a problem. Also, I continue to depend on the reading of the index & trees that unpack_trees() does, which I haven't modified, so again it'd be the same number of places that someone would need to fix. (However, the whole design to have unpack_trees() do the initial work and then have recursive merge try to "fix it up" is really starting to strain. Interesting point. I'm starting to think, again, that merge recursive needs a redesign, and have some arguments I wanted to float out there...but I've dumped enough on the list for a day.) It's possible that this series fixes one particular issue -- namely when merging, if the merge-base contained a "Test" directory, one side added a file to that directory, and the other side renamed "Test" to "test", and if the presence of both "Test" and "test" directories in the merge result is problematic, then at least with my fixes you wouldn't end up with both directories and could thus avoid that problem in a narrow set of cases. I'll think on that. It may provide extra clues as to what the right solutions could be! Sorry that I don't have any better news than that for you. Elijah Thanks -- Philip
Re: [PATCH 00/30] Add directory rename detection to git
On Fri, Nov 10, 2017 at 2:27 PM, Philip Oakleywrote: > From: "Elijah Newren" >> >> In this patchset, I introduce directory rename detection to >> merge-recursive, >> predominantly so that when files are added to directories on one side of >> history and those directories are renamed on the other side of history, >> the >> files will end up in the proper location after a merge or cherry-pick. >> >> However, this isn't limited to that simplistic case. More interesting >> possibilities exist, such as: >> >> * a file being renamed into a directory which is renamed on the other >>side of history, causing the need for a transitive rename. >> > > How does this cope with the case insensitive case preserving file systems on > Mac and Windows, esp when core.ignorecase is true. If it's a bigger problem > that the series already covers, would the likely changes be reasonably > localised? > > This came up recently on GfW for `git checkout` of a branch where the case > changed ("Test" <-> "test"), but git didn't notice that it needed to rename > the directories on such an file system. > https://github.com/git-for-windows/git/issues/1333 I wasn't aware there were problems with git on case insensitive case preserving filesystems; fixing them wasn't something I had in mind when writing this series. However, the particular bug you mention is actually completely orthogonal to this series; it talks about git-checkout without the -m/--merge option, which doesn't touch any code path I modified in my series, so my series can't really fix or worsen that particular issue. But, if there are further issues with such filesystems that also affect merges/cherry-picks/rebases, then I don't think my series will either help or hurt there either. The recursive merge machinery already has remove_file() and update_file() wrappers that it uses whenever it needs to remove/add/update a file in the working directory and/or index, and I have simply continued using those, so the number of places you'd need to modify to fix issues would remain just as localized as before. Also, I continue to depend on the reading of the index & trees that unpack_trees() does, which I haven't modified, so again it'd be the same number of places that someone would need to fix. (However, the whole design to have unpack_trees() do the initial work and then have recursive merge try to "fix it up" is really starting to strain. I'm starting to think, again, that merge recursive needs a redesign, and have some arguments I wanted to float out there...but I've dumped enough on the list for a day.) It's possible that this series fixes one particular issue -- namely when merging, if the merge-base contained a "Test" directory, one side added a file to that directory, and the other side renamed "Test" to "test", and if the presence of both "Test" and "test" directories in the merge result is problematic, then at least with my fixes you wouldn't end up with both directories and could thus avoid that problem in a narrow set of cases. Sorry that I don't have any better news than that for you. Elijah
Re: [PATCH 00/30] Add directory rename detection to git
From: "Elijah Newren"[This series is entirely independent of my rename detection limits series. However, I have a separate rename detection performance series that depends on both this series and the rename detection limits series.] In this patchset, I introduce directory rename detection to merge-recursive, predominantly so that when files are added to directories on one side of history and those directories are renamed on the other side of history, the files will end up in the proper location after a merge or cherry-pick. However, this isn't limited to that simplistic case. More interesting possibilities exist, such as: * a file being renamed into a directory which is renamed on the other side of history, causing the need for a transitive rename. How does this cope with the case insensitive case preserving file systems on Mac and Windows, esp when core.ignorecase is true. If it's a bigger problem that the series already covers, would the likely changes be reasonably localised? This came up recently on GfW for `git checkout` of a branch where the case changed ("Test" <-> "test"), but git didn't notice that it needed to rename the directories on such an file system. https://github.com/git-for-windows/git/issues/1333 -- Philip