Quote ' as \(aq in manpages

The docbook/xmlto toolchain insists on quoting ' as \'.  This does
achieve the quoting goal, but modern 'man' implementations turn the
apostrophe into a unicode "proper" apostrophe (given the right
circumstances), breaking code examples in many of our manpages.

Quote them as \(aq instead, which is an "apostrophe quote" as per the
groff_char manpage.

Unfortunately, as Anders Kaseorg kindly pointed out, this is not
portable beyond groff, so we add an extra Makefile variable GNU_ROFF
which you need to enable to get the new quoting.

Thanks also to Miklos Vajna for documentation.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/Makefile

@@ -103,6 +103,14 @@ ifdef DOCBOOK_SUPPRESS_SP
 XMLTO_EXTRA += -m manpage-suppress-sp.xsl
 endif
 
+# If your target system uses GNU groff, it may try to render
+# apostrophes as a "pretty" apostrophe using unicode.  This breaks
+# cut&paste, so you should set GNU_ROFF to force them to be ASCII
+# apostrophes.  Unfortunately does not work with non-GNU roff.
+ifdef GNU_ROFF
+XMLTO_EXTRA += -m manpage-quote-apos.xsl
+endif
+
 SHELL_PATH ?= $(SHELL)
 # Shell quote;
 SHELL_PATH_SQ = $(subst ','\'',$(SHELL_PATH))

Documentation/manpage-quote-apos.xsl

@@ -0,0 +1,16 @@
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+		version="1.0">
+
+<!-- work around newer groff/man setups using a prettier apostrophe
+     that unfortunately does not quote anything when cut&pasting
+     examples to the shell -->
+<xsl:template name="escape.apostrophe">
+  <xsl:param name="content"/>
+  <xsl:call-template name="string.subst">
+    <xsl:with-param name="string" select="$content"/>
+    <xsl:with-param name="target">'</xsl:with-param>
+    <xsl:with-param name="replacement">\(aq</xsl:with-param>
+  </xsl:call-template>
+</xsl:template>
+
+</xsl:stylesheet>

Makefile

@@ -142,6 +142,10 @@ all::
 #
 # Define DOCBOOK_XSL_172 if you want to format man pages with DocBook XSL v1.72.
 #
+# Define GNU_ROFF if your target system uses GNU groff.  This forces
+# apostrophes to be ASCII so that cut&pasting examples to the shell
+# will work.
+#
 # Define NO_PERL_MAKEMAKER if you cannot use Makefiles generated by perl's
 # MakeMaker (e.g. using ActiveState under Cygwin).
 #