os: provide a way to duplicate os.Root or, at least, clean up the base path when duplicating via relative path

[oakad]

Proposal Details

When dealing with os.Root, a need arises to pass it around to goroutines doing things. To simplify the lifecycle management, it will be the best to have an ability to duplicate the os.Root via a proper file descriptor duplication method, so each goroutine can close its own instance of os.Root when it's done.

In the meantime, duplication via OpenRoot(".") is available. Unfortunately, successive duplication don't carry the same name:

r1, _ := os.OpenRoot("/my/dir")
// r1.Name() == "/my/dir"

r2, _ := r1.OpenRoot(".")
// r2.Name() == "/my/dir/."

r3, _ := r2.OpenRoot(".")
// r3.Name() == "/my/dir/./."

One can, of course, always use filepath.Clean on the name returned, but then, so can the OpenRoot method internally.

[gabyhelp]

Related Issues

• proposal: os: add (*File).AsRoot() function that acts on os.File and returns *os.Root created from file/directory #75084 (closed)
• proposal: os: convenience function for one-off Root operations #73168
• proposal: os: extend Root FS with interface io/fs.SubFS #72054 (closed)

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[ianlancetaylor]

CC @neild

[neild]

If we did #70370, then this would be:

r1, _ := os.OpenRoot("root")
f, _ := r1.Open(".")
r2, _ := f.Root()

Alternatively, perhaps we should just have root.OpenRoot(".") preserve the root's name.

[oakad]

Root.AsFile will be most useful, yes. :-)