fix add overwrite race with git-annex add to annex

This is not a complete fix for all such races, only the one where a
large file gets changed while adding and gets added to git rather than
to the annex.

addLink needs to go away, any caller of it is probably subject to the
same kind of race. (Also, addLink itself fails to check gitignore when
symlinks are not supported.)

ingestAdd no longer checks gitignore. (It didn't check it consistently
before either, since there were cases where it did not run git add!)
When git-annex import calls it, it's already checked gitignore itself
earlier. When git-annex add calls it, it's usually on files found
by withFilesNotInGit, which handles checking ignores.

There was one other case, when git-annex add --batch calls it. In that
case, old git-annex behaved rather badly, it would seem to add the file,
but git add would later fail, leaving the file as an unstaged annex symlink.
That behavior has also been fixed.

Sponsored-by: Brett Eisenberg on Patreon

Command/Import.hs

@@ -246,7 +246,7 @@ startLocal o addunlockedmatcher largematcher mode (srcfile, destfile) =
 				}
 			}
 		ifM (checkFileMatcher largematcher destfile)
-			( ingestAdd' (checkGitIgnoreOption o) nullMeterUpdate (Just ld') (Just k)
+			( ingestAdd' nullMeterUpdate (Just ld') (Just k)
 				>>= maybe
 					stop
 					(\addedk -> next $ Command.Add.cleanup addedk True)