Update __fish_git_prompt.fish to handle git-svn better

Git-svn remotes can have a prefix for their remotes. If I set a prefix
of 'svn/' then my remote trunk branch is called svn/trunk. Update the
script to use the svn-remote.*.fetch key to figure out how the 'trunk'
branch is mapped into the remotes namespace and apply this to the
current branch. This assumes branches are mapped into the same
namespace, which is likely. It also doesn't work for tags, but neither
did the old code.

share/functions/__fish_git_prompt.fish

@@ -78,6 +78,7 @@
 function __fish_git_prompt_show_upstream --description "Helper function for __fish_git_prompt"
 	# Ask git-config for some config options
 	set -l svn_remote
+	set -l svn_prefix
 	set -l upstream git
 	set -l legacy
 	set -l verbose
@@ -90,6 +91,8 @@ function __fish_git_prompt_show_upstream --description "Helper function for __fi
 			test -n "$__fish_git_prompt_showupstream"; or return
 		case svn-remote.'*'.url
 			set svn_remote $svn_remote $value
+			set -l remote_prefix (/bin/sh -c 'echo "${1%.url}"' -- $key)
+			set svn_prefix $svn_prefix $remote_prefix
 			if test -n "$svn_url_pattern"
 				set svn_url_pattern $svn_url_pattern"\|$value"
 			else
@@ -122,8 +125,16 @@ function __fish_git_prompt_show_upstream --description "Helper function for __fi
 		if test (count $svn_upstream) -ne 0
 			echo $svn_upstream[-1] | read -l _ svn_upstream _
 			set svn_upstream (echo $svn_upstream | sed 's/@.*//')
-			for remote in $svn_remote
-				set svn_upstream (/bin/sh -c 'echo "${1#$2}"' -- $svn_upstream $remote)
+			set -l cur_prefix
+			for i in (seq (count $svn_remote))
+				set -l remote $svn_remote[$i]
+				set -l mod_upstream (/bin/sh -c 'echo "${1#$2}"' -- $svn_upstream $remote)
+				if test "$svn_upstream" != "$mod_upstream"
+					# we found a valid remote
+					set svn_upstream $mod_upstream
+					set cur_prefix $svn_prefix[$i]
+					break
+				end
 			end
 
 			if test -z "$svn_upstream"
@@ -139,6 +150,12 @@ function __fish_git_prompt_show_upstream --description "Helper function for __fi
 				else
 					set upstream $svn_upstream
 				end
+				set -l fetch_val (git config "$cur_prefix".fetch)
+				if test -n "$fetch_val"
+					set -l IFS :
+					echo "$fetch_val" | read -l trunk pattern
+					set upstream (/bin/sh -c 'echo "${1%/$2}"' -- $pattern $trunk)/$upstream
+				end
 			end
 		else
 			if test $upstream = svn+git