sync --all avoid unncessary first pass

Sped up seeking to around twice as fast, by avoiding a pass over the
worktree files when preferred content expressions of the local repo and
remotes don't use include=/exclude=.

Thanks to Lukey for identifying the optimisation.

This commit was sponsored by Brock Spratlen on Patreon.

doc/todo/skip_first_pass_in_git_annex_sync.mdwn

@@ -19,3 +19,5 @@ and it led to a 2x speedup (with warm cache):
 
 
 This repo has 25641 keys and all of them are in the worktree too.
+
+> [[done]]! --[[Joey]]

doc/todo/skip_first_pass_in_git_annex_sync/comment_2_9a93d321f955c3cdac5b8cbcd452f42e._comment

@@ -0,0 +1,15 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2020-09-24T19:04:32Z"
+ content="""
+One side effect of this optimisation is that, while sync --all used to
+tell the filenames it was getting or dropping, when operating on files
+in the working tree, when the optimsation is enabled it will only
+display the keys. So, its behavior in 2 different repos might seem
+inconsistent to a user, who doesn't know about all these gory 2 pass details.
+
+I think, if that became a problem, the best fix would be to only display
+the keys, and never the worktree filenames, even when running the first
+pass. But I'll wait and see if that needs to be done, I suppose.
+"""]]