tests: prepend to PATH with $PATH_SEP, not a literal ":"

Several tests make a script in the current directory findable by
git-spawned helpers (a fake gpg, a fake editor, ...) by prepending $PWD
to PATH as `PATH="$PWD:$PATH"`. The literal ":" is the POSIX path-list
separator, which is what the MSYS2 Bash uses, but BusyBox' ash speaks to
Win32 directly and its PATH is ";"-separated. The hardcoded ":" then
glues $PWD onto the first real entry, so for instance t7510's
`gpg.program=fake-gpg` can no longer be found and the commit aborts with
"cannot spawn fake-gpg: No such file or directory".

test-lib already computes the correct separator in $PATH_SEP (";" when
the inherited PATH contains one, ":" otherwise); use it. This is a no-op
for the existing POSIX and MSYS2 callers and fixes the BusyBox runs.

Assisted-by: Opus 4.8
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

t/t3430-rebase-merges.sh

@@ -234,7 +234,7 @@ test_expect_success 'merge -c rewords when a strategy is given' '
 	git add G.t
 	EOF
 
-	PATH="$PWD:$PATH" \
+	PATH="$PWD$PATH_SEP$PATH" \
 	GIT_SEQUENCE_EDITOR="echo merge -c H G >" \
 	GIT_EDITOR="echo edited >>" \
 		git rebase --no-ff -ir -s override -Xxopt E &&
@@ -570,7 +570,7 @@ test_expect_success '--rebase-merges with strategies' '
 	echo overridden$1 >>G.t
 	git add G.t
 	EOF
-	PATH="$PWD:$PATH" git rebase -ir -s override -Xxopt G &&
+	PATH="$PWD$PATH_SEP$PATH" git rebase -ir -s override -Xxopt G &&
 	test_write_lines G overridden--xopt >expect &&
 	test_cmp expect G.t
 '

t/t5801-remote-helpers.sh

@@ -350,7 +350,7 @@ test_expect_success 'totally broken helper reports failure message' '
 	exit 1
 	EOF
 	test_must_fail \
-		env PATH="$PWD:$PATH" \
+		env PATH="$PWD$PATH_SEP$PATH" \
 		git clone broken://example.com/foo.git 2>stderr &&
 	grep aborted stderr
 '

t/t7005-editor.sh

@@ -58,7 +58,7 @@ do
 				export $i
 				;;
 			esac &&
-			PATH="$PWD:$PATH" TERM=vt100 git commit --amend
+			PATH="$PWD$PATH_SEP$PATH" TERM=vt100 git commit --amend
 		) &&
 		test_commit_message HEAD -m "Edited by $i"
 	'
@@ -80,7 +80,7 @@ test_expect_success 'Using editors with overrides' '
 				export $i
 				;;
 			esac &&
-			PATH="$PWD:$PATH" git commit --amend &&
+			PATH="$PWD$PATH_SEP$PATH" git commit --amend &&
 			test_commit_message HEAD expect || exit 1
 		done
 	)

t/t7510-signed-commit.sh

@@ -458,7 +458,7 @@ test_expect_success 'custom `gpg.program`' '
 
 	# `gpg.program` does not specify an absolute path, it should find a program in `$PATH`
 	test_config gpg.program "fake-gpg" &&
-	env PATH="$PWD:$PATH" \
+	env PATH="$PWD$PATH_SEP$PATH" \
 	git commit -S --allow-empty -m signed-commit
 '
 

t/t9001-send-email.sh

@@ -2621,7 +2621,7 @@ test_expect_success $PREREQ 'mailmap support in Cc header' '
 
 test_expect_success $PREREQ 'test using command name with --sendmail-cmd' '
 	clean_fake_sendmail &&
-	PATH="$PWD:$PATH" \
+	PATH="$PWD$PATH_SEP$PATH" \
 	git send-email \
 		--from="Example <nobody@example.com>" \
 		--to=nobody@example.com \