diff --git a/t/lib-credential.sh b/t/lib-credential.sh
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new mode 100644
index bb88cc0108..dea2cbef51
--- a/t/lib-credential.sh
+++ b/t/lib-credential.sh
@@ -1,4 +1,5 @@
-#!/bin/sh
+# Shell library for testing credential handling including helpers. See t0302
+# for an example of testing a specific helper.
 
 # Try a set of credential helpers; the expected stdin,
 # stdout and stderr should be provided on stdin,
diff --git a/t/lib-gpg.sh b/t/lib-gpg.sh
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new mode 100644
diff --git a/t/lib-log-graph.sh b/t/lib-log-graph.sh
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diff --git a/t/lib-submodule-update.sh b/t/lib-submodule-update.sh
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