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po/insert-header.sin

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+# Sed script that inserts the file called HEADER before the header entry.
+#
+# At each occurrence of a line starting with "msgid ", we execute the following
+# commands. At the first occurrence, insert the file. At the following
+# occurrences, do nothing. The distinction between the first and the following
+# occurrences is achieved by looking at the hold space.
+/^msgid /{
+x
+# Test if the hold space is empty.
+s/m/m/
+ta
+# Yes it was empty. First occurrence. Read the file.
+r HEADER
+# Output the file's contents by reading the next line. But don't lose the
+# current line while doing this.
+g
+N
+bb
+:a
+# The hold space was nonempty. Following occurrences. Do nothing.
+x
+:b
+}