webapp: Generate better git remote names.

Wrote a better git remote name sanitizer. Git blows up on lots of weird
stuff, especially if it starts the remote name, but I managed to get
some common punctuation working.

Git/Remote.hs

@@ -0,0 +1,33 @@
+{- git remote stuff
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+module Git.Remote where
+
+import Common
+import Data.Char
+
+{- Construct a legal git remote name out of an arbitrary input string.
+ -
+ - There seems to be no formal definition of this in the git source,
+ - just some ad-hoc checks, and some other things that fail with certian
+ - types of names (like ones starting with '-').
+ -}
+makeLegalName :: String -> String
+makeLegalName s = case filter legal $ replace "/" "_" s of
+	-- it can't be empty
+	[] -> "unnamed"
+	-- it can't start with / or - or .
+	'.':s' -> makeLegalName s'
+	'/':s' -> makeLegalName s'
+	'-':s' -> makeLegalName s'
+	s' -> s'
+  where
+	{- Only alphanumerics, and a few common bits of punctuation common
+	 - in hostnames. -}
+	legal '_' = True
+	legal '.' = True
+	legal c = isAlphaNum c