Fix Windows-specific problem to determine the real path near a drive root #4253
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It is possible (and supported) that `strbuf_realpath()` can work in-place, i.e. the second parameter passed to the function can refer to the `buf` field of the first parameter. Our code was ill-prepared for that, though: we first store a pointer to the last component (that does not necessarily need to exist) before calling the `GetFinalPathNameByHandleW()` function. Said function is totally allowed to produce a longer path than the original one (e.g. by prefixing it with `\\?\`, a relatively unintuitive Windows-only concept). Which would overwrite the last component part. Address that by making a full string copy of the last component. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Let's be careful to make this function work near the drive root: to resolve the drive root path itself, we _need_ a trailing backslash: if a file handle to the path `C:` is created, it does not actually refer to the drive root. Instead, it refers to this very Windows-only concept of a "per-drive current directory". This also requires the code that wants to re-append the last component to be more careful and only append a slash _if necessary_. This commit fixes the problem with `scalar unregister C:/foo` that was reported at git-for-windows#4200. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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derrickstolee
approved these changes
Jan 27, 2023
Merged
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This PR fixes a pretty fundamental problem where
win32_strbuf_realpath()mishandled non-existing paths that are close to the drive root, e.g.C:/foo.This fixes #4200