refactor(git): centralise the git:// scheme behind util.uri / util.parse_uri

lua/git/util.lua

@@ -1,5 +1,21 @@
 local M = {}
 
+local URI_PREFIX = "git://"
+
+---@param revspec string
+---@return string
+function M.uri(revspec)
+    return URI_PREFIX .. revspec
+end
+
+---Extract the revspec from a `git://<revspec>` buffer name. Returns
+---nil if the name doesn't carry the scheme.
+---@param name string
+---@return string?
+function M.parse_uri(name)
+    return name:match("^" .. URI_PREFIX .. "(.+)$")
+end
+
 ---@class ow.Git.ParsedRevspec
 ---@field stage 0|1|2|3?  index stage when the revspec is `:<path>` / `:0:<path>` / `:N:<path>`; nil otherwise
 ---@field path string?    path component when the revspec carries one; nil for bare object refs