sync: When some remotes to sync with are specified, and --fast is too, pick the lowest cost of the specified remotes

Do not sync with a faster remote that was not specified.

That old behavior was only documented in the changelog, and was certianly
surprising. It also meant adding --fast made it slower..

CHANGELOG

@@ -31,6 +31,9 @@ git-annex (8.20200331) UNRELEASED; urgency=medium
     git-annex enableremote is passed readonly=true.
   * Stop storing readonly=true in remote.log of external special remotes;
     it is a local setting only.
+  * sync: When some remotes to sync with are specified, and --fast is too,
+    pick the lowest cost of the specified remotes, do not sync with a
+    faster remote that was not specified.
 
  -- Joey Hess <id@joeyh.name>  Mon, 30 Mar 2020 15:58:34 -0400
 

Command/Sync.hs

@@ -291,10 +291,8 @@ syncRemotes ps = do
 
 syncRemotes' :: [String] -> [Remote] -> Annex [Remote]
 syncRemotes' ps available = 
-	ifM (Annex.getState Annex.fast) ( nub <$> pickfast , wanted )
+	ifM (Annex.getState Annex.fast) ( fastest <$> wanted , wanted )
   where
-	pickfast = (++) <$> listed <*> (filterM good (fastest available))
-	
 	wanted
 		| null ps = filterM good (concat $ Remote.byCost available)
 		| otherwise = listed

doc/bugs/git_annex_sync__58___--fast_and_REMOTE_should_be_exclusive.mdwn

@@ -22,3 +22,5 @@ I actually used `--fast` because I was annoyed by annex iterating over all files
 ### What version of git-annex are you using? On what operating system?
 
 8.20200330, Debian testing
+
+> [[fixed|done]] --[[Joey]]

doc/git-annex-sync.mdwn

@@ -46,6 +46,9 @@ received.
 
   Only sync with the remotes with the lowest annex-cost value configured.
 
+  When a list of remotes (or remote groups) is provided, it picks from
+  amoung those, otherwise it picks from amoung all remotes.
+
 * `--only-annex` `-a`, `--not-only-annex`
 
   Only sync the git-annex branch and annexed content with remotes,