shells/fish: cherry-pick upstream fix for SVN performance

Upstream bug #6681 causes fish to run _very_ slowly inside of large
Subversion repositories.  The bug will be fixed in release 3.1.1.  But it's
worthwhile to cherry-pick the fix since all FreeBSD developers use large
Subversion repositories.

fish-shell/fish-shell#6681


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@532045 35697150-7ecd-e111-bb59-0022644237b5

shells/fish/Makefile

@@ -3,6 +3,7 @@
 
 PORTNAME=	fish
 PORTVERSION=	3.1.0
+PORTREVISION=	1
 CATEGORIES=	shells
 MASTER_SITES=	https://github.com/fish-shell/fish-shell/releases/download/${PORTVERSION}/
 

shells/fish/files/patch-share_functions_fish__vcs__prompt.fish

@@ -0,0 +1,12 @@
+--- share/functions/fish_vcs_prompt.fish.orig	2020-04-18 20:32:19 UTC
++++ share/functions/fish_vcs_prompt.fish
+@@ -3,5 +3,8 @@ function fish_vcs_prompt --description "Print the prom
+     # This is so we don't try svn if git already worked.
+     fish_git_prompt
+     or fish_hg_prompt
+-    or fish_svn_prompt
++    # The svn prompt is disabled by default because it's quite slow on common svn repositories.
++    # To enable it uncomment it.
++    # You can also only use it in specific directories by checking $PWD.
++    # or fish_svn_prompt
+ end