git-prompt.sh: optionally show upstream branch name

When working with multiple remotes, it is common to switch the upstream
from a remote to another. Doing so, the prompt may not be the expected
one. Providing an option to display tracking information sounds useful.

Add a "name" option to GIT_PS1_SHOWUPSTREAM which will show the upstream
abbrev name. This option is ignored if "verbose" is false.

Signed-off-by: Julien Carsique <julien.carsique@gmail.com>
Improved-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

Author: jcarsique

contrib/completion/git-prompt.sh

@@ -60,6 +60,7 @@
 # of values:
 #
 #     verbose       show number of commits ahead/behind (+/-) upstream
+#     name          if verbose, then also show the upstream abbrev name
 #     legacy        don't use the '--count' option available in recent
 #                   versions of git-rev-list
 #     git           always compare HEAD to @{upstream}
@@ -94,7 +95,7 @@ __git_ps1_show_upstream ()
 {
 	local key value
 	local svn_remote svn_url_pattern count n
-	local upstream=git legacy="" verbose=""
+	local upstream=git legacy="" verbose="" name=""
 
 	svn_remote=()
 	# get some config options from git-config
@@ -122,6 +123,7 @@ __git_ps1_show_upstream ()
 		git|svn) upstream="$option" ;;
 		verbose) verbose=1 ;;
 		legacy)  legacy=1  ;;
+		name)    name=1 ;;
 		esac
 	done
 
@@ -204,6 +206,9 @@ __git_ps1_show_upstream ()
 		*)	    # diverged from upstream
 			p=" u+${count#*	}-${count%	*}" ;;
 		esac
+		if [[ -n "$count" && -n "$name" ]]; then
+			p="$p $(git rev-parse --abbrev-ref "$upstream" 2>/dev/null)"
+		fi
 	fi
 
 }