Single dot (.) as password name is invalid

[jgrocho]

In my password store I have a file named path/to/file/..gpg. On Windows and Linux clients this correctly appears as path/to/file/., but in Pass for iOS it doesn’t appear at all. Investigation revealed that adding a password with the name . works at the top level, but doesn’t work in any subdirectory (this is also the case for a name of ..). I get that . and .. are reserved words in the file system and shouldn’t appear as components in the path, but they should be allowed for the final component since .gpg gets appended.