Filesystem

Cargo tends to get run on a very wide array of file systems. Different file systems can have a wide range of capabilities, and Cargo should strive to do its best to handle them. Some examples of issues to deal with:

• Not all file systems support locking. Cargo tries to detect if locking is supported, and if not, will ignore lock errors. This isn't ideal, but it is difficult to deal with.
• The fs::canonicalize function doesn't work on all file systems (particularly some Windows file systems). If that function is used, there should be a fallback if it fails. This function will also return \\?\ style paths on Windows, which can have some issues (such as some tools not supporting them, or having issues with relative paths).
• Timestamps can be unreliable. The fingerprint module has a deeper discussion of this. One example is that Docker cache layers will erase the fractional part of the time stamp.
• Symlinks are not always supported, particularly on Windows.