git-prompt: show presence of unresolved conflicts at command prompt

If GIT_PS1_SHOWCONFLICTSTATE is set to "yes", show the word "CONFLICT"
on the command prompt when there are unresolved conflicts.

Example prompt: (main|CONFLICT)

Signed-off-by: Justin Donnelly <justinrdonnelly@gmail.com>

contrib/completion/git-prompt.sh

@@ -84,6 +84,10 @@
 # single '?' character by setting GIT_PS1_COMPRESSSPARSESTATE, or omitted
 # by setting GIT_PS1_OMITSPARSESTATE.
 #
+# If you would like to see a notification on the prompt when there are
+# unresolved conflicts, set GIT_PS1_SHOWCONFLICTSTATE to "yes". The
+# prompt will include "|CONFLICT".
+#
 # If you would like to see more information about the identity of
 # commits checked out as a detached HEAD, set GIT_PS1_DESCRIBE_STYLE
 # to one of these values:
@@ -508,6 +512,12 @@ __git_ps1 ()
 		r="$r $step/$total"
 	fi
 
+	local conflict="" # state indicator for unresolved conflicts
+	if [[ "${GIT_PS1_SHOWCONFLICTSTATE}" == "yes" ]] &&
+	   [[ $(git ls-files --unmerged 2>/dev/null) ]]; then
+		conflict="|CONFLICT"
+	fi
+
 	local w=""
 	local i=""
 	local s=""
@@ -572,7 +582,7 @@ __git_ps1 ()
 	fi
 
 	local f="$h$w$i$s$u$p"
-	local gitstring="$c$b${f:+$z$f}${sparse}$r${upstream}"
+	local gitstring="$c$b${f:+$z$f}${sparse}$r${upstream}${conflict}"
 
 	if [ $pcmode = yes ]; then
 		if [ "${__git_printf_supports_v-}" != yes ]; then

t/t9903-bash-prompt.sh

@@ -188,7 +188,23 @@ test_expect_success 'prompt - rebase merge' '
 	test_when_finished "git checkout main" &&
 	test_must_fail git rebase --merge b1 b2 &&
 	test_when_finished "git rebase --abort" &&
-	__git_ps1 >"$actual" &&
+	(
+		sane_unset GIT_PS1_SHOWCONFLICTSTATE &&
+		__git_ps1 >"$actual"
+	) &&
+	test_cmp expected "$actual"
+'
+
+test_expect_success 'prompt - rebase merge conflict' '
+	printf " (b2|REBASE 1/3|CONFLICT)" >expected &&
+	git checkout b2 &&
+	test_when_finished "git checkout main" &&
+	test_must_fail git rebase --merge b1 b2 &&
+	test_when_finished "git rebase --abort" &&
+	(
+		GIT_PS1_SHOWCONFLICTSTATE="yes" &&
+		__git_ps1 >"$actual"
+	) &&
 	test_cmp expected "$actual"
 '
 
@@ -198,7 +214,23 @@ test_expect_success 'prompt - rebase am' '
 	test_when_finished "git checkout main" &&
 	test_must_fail git rebase --apply b1 b2 &&
 	test_when_finished "git rebase --abort" &&
-	__git_ps1 >"$actual" &&
+	(
+		sane_unset GIT_PS1_SHOWCONFLICTSTATE &&
+		__git_ps1 >"$actual"
+	) &&
+	test_cmp expected "$actual"
+'
+
+test_expect_success 'prompt - rebase am conflict' '
+	printf " (b2|REBASE 1/3|CONFLICT)" >expected &&
+	git checkout b2 &&
+	test_when_finished "git checkout main" &&
+	test_must_fail git rebase --apply b1 b2 &&
+	test_when_finished "git rebase --abort" &&
+	(
+		GIT_PS1_SHOWCONFLICTSTATE="yes" &&
+		__git_ps1 >"$actual"
+	) &&
 	test_cmp expected "$actual"
 '
 
@@ -208,22 +240,52 @@ test_expect_success 'prompt - merge' '
 	test_when_finished "git checkout main" &&
 	test_must_fail git merge b2 &&
 	test_when_finished "git reset --hard" &&
-	__git_ps1 >"$actual" &&
+	(
+		sane_unset GIT_PS1_SHOWCONFLICTSTATE &&
+		__git_ps1 >"$actual"
+	) &&
+	test_cmp expected "$actual"
+'
+
+test_expect_success 'prompt - merge conflict' '
+	printf " (b1|MERGING|CONFLICT)" >expected &&
+	git checkout b1 &&
+	test_when_finished "git checkout main" &&
+	test_must_fail git merge b2 &&
+	test_when_finished "git reset --hard" &&
+	(
+		GIT_PS1_SHOWCONFLICTSTATE="yes" &&
+		__git_ps1 >"$actual"
+	) &&
 	test_cmp expected "$actual"
 '
 
 test_expect_success 'prompt - cherry-pick' '
 	printf " (main|CHERRY-PICKING)" >expected &&
 	test_must_fail git cherry-pick b1 b1^ &&
 	test_when_finished "git cherry-pick --abort" &&
-	__git_ps1 >"$actual" &&
+	(
+		sane_unset GIT_PS1_SHOWCONFLICTSTATE &&
+		__git_ps1 >"$actual"
+	) &&
 	test_cmp expected "$actual" &&
 	git reset --merge &&
 	test_must_fail git rev-parse CHERRY_PICK_HEAD &&
 	__git_ps1 >"$actual" &&
 	test_cmp expected "$actual"
 '
 
+test_expect_success 'prompt - cherry-pick conflict' '
+	printf " (main|CHERRY-PICKING|CONFLICT)" >expected &&
+	test_must_fail git cherry-pick b1 b1^ &&
+	test_when_finished "git cherry-pick --abort" &&
+	(
+		GIT_PS1_SHOWCONFLICTSTATE="yes" &&
+		__git_ps1 >"$actual"
+	) &&
+	test_cmp expected "$actual"
+'
+
 test_expect_success 'prompt - revert' '
 	printf " (main|REVERTING)" >expected &&
 	test_must_fail git revert b1^ b1 &&