Documentation: sort sources for gitman.texi

Sorting the sources makes it easier to compare the output using diff.
In addition, it aids groups creating reproducible builds, as the order
of the files is no longer dependent on the file system or other
irrelevant factors.

Signed-off-by: brian m. carlson <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: bk2204

Documentation/Makefile

@@ -373,7 +373,7 @@ user-manual.pdf: user-manual.xml
 
 gitman.texi: $(MAN_XML) cat-texi.perl
 	$(QUIET_DB2TEXI)$(RM) $@+ $@ && \
-	($(foreach xml,$(MAN_XML),$(DOCBOOK2X_TEXI) --encoding=UTF-8 \
+	($(foreach xml,$(sort $(MAN_XML)),$(DOCBOOK2X_TEXI) --encoding=UTF-8 \
 		--to-stdout $(xml) &&) true) > $@++ && \
 	$(PERL_PATH) cat-texi.perl $@ <$@++ >$@+ && \
 	rm $@++ && \