Refuse to write to reserved filenames #2440
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In the next commit, we want to disallow accessing any path that contains any segment that is equivalent to `NUL`. In particular, we want to disallow accessing `NUL` (e.g. to prevent any repository from being checked out that contains a file called `NUL`, as that is not a valid file name on Windows). However, there are legitimate use cases within Git itself to write to the Null device. As Git is really a Linux project, it does not abstract that idea, though, but instead uses `/dev/null` to describe this intention. So let's side-step the validation _specifically_ in the case that we want to write to (or read from) `/dev/null`, via a dedicated short-cut in the code that skips the call to `validate_win32_path()`. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
There are a couple of reserved names that cannot be file names on Windows, such as `AUX`, `NUL`, etc. For an almost complete list, see https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file If one would try to create a directory named `NUL`, it would actually "succeed", i.e. the call would return success, but nothing would be created. Worse, even adding a file extension to the reserved name does not make it a valid file name. To understand the rationale behind that behavior, see https://devblogs.microsoft.com/oldnewthing/20031022-00/?p=42073 Let's just disallow them all. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This topic branch refuses to create files with reserved file names, such as `aux.c` or `nul.txt`. This addresses git-for-windows#679. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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This is a companion PR to gitgitgadget#496 (including a merge commit needed to sort out merge conflicts with the
core.longPathsfeature).On Windows, for historical reasons, file names such as
aux.c,nul.txtare not allowed. Foraux.c, attempts to write such a file will result in an obscure error, fornul.txtthe call will succeed but no such file will appear, ever, instead the effect will be equivalent to writing to/dev/nullon Linux/Unix.Let's help users by refusing to create such files altogether, with an informative error message.
This addresses #679 and supersedes #686