Writing to a memfs file does not update modtime

[hansbogert]

Bug Description

Modtimes never seem to update upon write.

go-git Version

latest

Steps to Reproduce

Please see added test here:

hansbogert@429cdfb

Additional Information

No response

[pjbgf]

@hansbogert thanks for raising this issue.

Feel free to propose a PR adding the test and the fix for this. This is likely a regression from this, which fixed the previous non-deterministic behaviour.

[hansbogert]

@pjbgf what is the reason to have this duplicate(...) here:

go-billy/memfs/memory.go

Line 74 in 56610a8

return f.Duplicate(filename, perm, flag), nil

?

[pjbgf]

@hansbogert I believe this is to avoid concurrency issues. Multiple callers of Open should not affect each other - to some extent. For example, if I have two concurrent calls to Open for the same file, caller A should not affect the file.position from caller B, and vice-versa - otherwise we would have a race condition.

[hansbogert]

Fixed in #152