[PATCH v2 4/5] git-mergetool--lib.sh: add error message for unknown tool variant

["Philippe Blain via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Philippe Blain <levraiphilippeblain@xxxxxxxxx>

In setup_tool, we check if the given tool is a known variant of a tool,
and quietly return with an error if not. This leads to the following
invocation quietly failing:

	git mergetool --tool=vimdiff4

Add an error message before returning in this case.

Signed-off-by: Philippe Blain <levraiphilippeblain@xxxxxxxxx>
---
 git-mergetool--lib.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index d7e410d9481..11ea181259f 100644
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -264,6 +264,7 @@ setup_tool () {
 
 	if ! list_tool_variants | grep -q "^$tool$"
 	then
+		echo "error: unknown tool variant '$tool'" >&2
 		return 1
 	fi
 
-- 
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