simplify setup process for minimal config mode

Allow cloning a branch.

Updated wrapper to check for propellor.cabal and not try to update
if it's not present, to handle this case.

doc/components.mdwn

@@ -24,20 +24,9 @@ then copy in `~/.propellor/src/Propellor/` and it will be used. See
 [[contributing]] if you want to send your improvements back.
 
 All that really needs to be in `~/.propellor/` though, is a `config.hs`
-file, and a cabal file. If you want to set up the repository manually,
-and don't want it to contain propellor's source code, here's a stub cabal
-file to get you started:
+file, and a cabal file. To use propellor this way, you can first
+install propellor, and then copy the two files from the
+[mininalconfig branch](http://source.propellor.branchable.com/?p=source.git;a=tree;h=refs/heads/minimalconfig;hb=refs/heads/minimalconfig),
+or clone it:
 
-<pre>
-Name: foo
-Cabal-Version: >= 1.6
-Build-Type: Simple
-Version: 0
-
-Executable propellor-config
-  Main-Is: config.hs
-  GHC-Options: -Wall -threaded -O0
-  Build-Depends: propellor, base >= 3
-</pre>
-
-See [[haskell_newbie]] for an example config.hs file.
+	git clone ssh://b-propellor@propellor.branchable.com/propellor.branchable.com .propellor --branch minimalconfig --single-branch

src/wrapper.hs

@@ -77,7 +77,7 @@ wrapper args propellordir propellorbin = do
 			, void $ boolSystem "git" [Param "clone", Param netrepo, File propellordir]
 			)
 
-	checkRepo = whenM (doesFileExist disthead) $ do
+	checkRepo = whenM (doesFileExist disthead <&&> doesFileExist (propellordir </> "propellor.cabal")) $ do
 		headrev <- takeWhile (/= '\n') <$> readFile disthead
 		changeWorkingDirectory propellordir
 		headknown <- catchMaybeIO $