Illegal filenames on Windows

[AgentD]

On Windows, some filenames are forbidden, e.g. ones containing characters like : or name/extensions like CON.

Currently, rdsquashfs checks for those when unpacking an archive and refuses to create such entries. According to an e-mail exchange I had recently, there are other programs that work around this by mapping illegal characters into the Unicode Private Use Area (e.g. : = 0x3a becomes 0xf03a). There is also a port of squashfs-tools for Windows floating around that does this transparently. No idea what they do with files named CON, but it sounds like an interesting feature to have, allowing full round tripping on Windows without going through tar and Winrar/7zip.

Here are some thoughts I had so far:

• Doing this must require an option to be enabled. Doing it transparently by default breaks use cases where someone actually uses the PUA.
• Illegal names like CON could be broken up by inserting an _?
• TODO: Are there any potential reasons for Windows/Winapi to get angry if we do this?
• Theoretically, it should be enough to have this in rdsquashfs. It can generate a manifest file (with --describe) that has the original names and remapped file source paths, allowing gensquashfs to pack it with the original names without knowing of this trick.

[AgentD]

I have pushed 3 commits to the new 1.3.0 branch, implementing this feature.

Signed test builds from b4d5c76:

squashfs-tools-ng-1.2.0-mingw32.zip squashfs-tools-ng-1.2.0-mingw64.zip

GPG signatures for the archives:

signatures.zip

EDIT: Bump build to newer commit