Avoid throwing fatal errors when asked to write to a readonly git remote on http

Test suite found one of them, looking for giveup turned up several more.

CHANGELOG

@@ -4,6 +4,8 @@ git-annex (7.20200205) UNRELEASED; urgency=medium
     caching, default annex.sshcaching to false, but let the user override it.
   * Improve warning messages further when ssh connection caching cannot
     be used, to clearly state why.
+  * Avoid throwing fatal errors when asked to write to a readonly
+    git remote on http.
 
  -- Joey Hess <id@joeyh.name>  Fri, 14 Feb 2020 14:12:25 -0400
 

Remote/Git.hs

@@ -432,7 +432,9 @@ dropKey' repo r (State connpool duc _ _) key
 				return True
 		, return False
 		)
-	| Git.repoIsHttp repo = giveup "dropping from http remote not supported"
+	| Git.repoIsHttp repo = do
+		warning "dropping from http remote not supported"
+		return False
 	| otherwise = commitOnCleanup repo r $ do
 		let fallback = Ssh.dropKey repo key
 		P2PHelper.remove (Ssh.runProto r connpool (return False) fallback) key
@@ -536,7 +538,9 @@ copyFromRemote'' repo forcersync r st@(State connpool _ _ _) key file dest meter
 		else P2PHelper.retrieve
 			(\p -> Ssh.runProto r connpool (return (False, UnVerified)) (fallback p))
 			key file dest meterupdate
-	| otherwise = giveup "copying from non-ssh, non-http remote not supported"
+	| otherwise = do
+		warning "copying from non-ssh, non-http remote not supported"
+		unVerified (return False)
   where
 	fallback p = unVerified $ feedprogressback $ \p' -> do
 		oh <- mkOutputHandlerQuiet
@@ -649,7 +653,9 @@ copyToRemote' repo r st@(State connpool duc _ _) key file meterupdate
 			(\p -> Ssh.runProto r connpool (return False) (copyremotefallback p))
 			key file meterupdate
 		
-	| otherwise = giveup "copying to non-ssh repo not supported"
+	| otherwise = do
+		warning "copying to non-ssh repo not supported"
+		return False
   where
 	copylocal Nothing = return False
 	copylocal (Just (object, checksuccess)) = do

doc/bugs/Remote_Tests__58___storeKey_fails_for_http_remotes___40__skip_instead__63____41__.mdwn

@@ -78,3 +78,8 @@ It's possible there's another issue here I'm not entirely aware of.
 ### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)
 
 Of course!  I use and rely on it daily :)
+
+> This is not a bug in the test suite, it turns out, but in
+> git-annex's handling of a http remote. It was throwing fatal errors
+> rather than the correct behavior of displaying a warning. [[fixed|done]]
+> --[[Joey]]