git-prompt: make upstream state indicator location consistent

Make upstream state indicator location more consistent with similar
state indicators (e.g. sparse). Group the short upstream state indicator
(`=`, `<`, `>`, or `<>`) with other short state indicators immediately
after the branch name. Previously short and long upstream state
indicators appeared after all other state indicators.

Use a separator (`SP` or `GIT_PS1_STATESEPARATOR`) between branch name
and short upstream state indicator. Previously the short upstream state
indicator would sometimes appear directly adjacent to the branch name
instead of being separated.

For comparison, `__git_ps1` examples without upstream state indicator:
(main)
(main %)
(main *%)
(main|SPARSE)
(main %|SPARSE)
(main *%|SPARSE)
(main|SPARSE|REBASE 1/2)
(main %|SPARSE|REBASE 1/2)

Note that if there are short state indicators, they appear together
after the branch name and separated from it by `SP` or
`GIT_PS1_STATESEPARATOR`.

Before/after examples with short upstream state indicator:
| Before           | After            |
| ---------------- | ---------------- |
| (main=)          | (main =)         |
| (main|SPARSE=)   | (main =|SPARSE)  |
| (main %|SPARSE=) | (main %=|SPARSE) |

Signed-off-by: Justin Donnelly <justinrdonnelly@gmail.com>
Reviewed-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-prompt.sh

@@ -109,7 +109,7 @@
 __git_printf_supports_v=
 printf -v __git_printf_supports_v -- '%s' yes >/dev/null 2>&1
 
-# stores the divergence from upstream in $p
+# stores the divergence from upstream in $p (for short status) or $upstream (for verbose status)
 # used by GIT_PS1_SHOWUPSTREAM
 __git_ps1_show_upstream ()
 {
@@ -214,26 +214,26 @@ __git_ps1_show_upstream ()
 		*)	    # diverged from upstream
 			p="<>" ;;
 		esac
-	else
+	else # verbose, set upstream instead of p
 		case "$count" in
 		"") # no upstream
-			p="" ;;
+			upstream="" ;;
 		"0	0") # equal to upstream
-			p=" u=" ;;
+			upstream=" u=" ;;
 		"0	"*) # ahead of upstream
-			p=" u+${count#0	}" ;;
+			upstream=" u+${count#0	}" ;;
 		*"	0") # behind upstream
-			p=" u-${count%	0}" ;;
+			upstream=" u-${count%	0}" ;;
 		*)	    # diverged from upstream
-			p=" u+${count#*	}-${count%	*}" ;;
+			upstream=" u+${count#*	}-${count%	*}" ;;
 		esac
 		if [[ -n "$count" && -n "$name" ]]; then
 			__git_ps1_upstream_name=$(git rev-parse \
 				--abbrev-ref "$upstream_type" 2>/dev/null)
 			if [ $pcmode = yes ] && [ $ps1_expanded = yes ]; then
-				p="$p \${__git_ps1_upstream_name}"
+				upstream="$upstream \${__git_ps1_upstream_name}"
 			else
-				p="$p ${__git_ps1_upstream_name}"
+				upstream="$upstream ${__git_ps1_upstream_name}"
 				# not needed anymore; keep user's
 				# environment clean
 				unset __git_ps1_upstream_name
@@ -512,7 +512,8 @@ __git_ps1 ()
 	local u=""
 	local h=""
 	local c=""
-	local p=""
+	local p="" # short version of upstream state indicator
+	local upstream="" # verbose version of upstream state indicator
 
 	if [ "true" = "$inside_gitdir" ]; then
 		if [ "true" = "$bare_repo" ]; then
@@ -568,8 +569,8 @@ __git_ps1 ()
 		b="\${__git_ps1_branch_name}"
 	fi
 
-	local f="$h$w$i$s$u"
-	local gitstring="$c$b${f:+$z$f}${sparse}$r$p"
+	local f="$h$w$i$s$u$p"
+	local gitstring="$c$b${f:+$z$f}${sparse}$r${upstream}"
 
 	if [ $pcmode = yes ]; then
 		if [ "${__git_printf_supports_v-}" != yes ]; then