[PATCH] build: do not require help2man at build-from-tarball time

[Jim Meyering]

We can't have build-from-tarball requiring perl (via help2man)
or regenerating a distributed .1 file when its .c file has not changed.

>From 57da212a95054cc230ffb00f38ea655c798926f8 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Sun, 9 Sep 2012 19:27:25 +0200
Subject: [PATCH] build: do not require help2man at build-from-tarball time

But do retain full dependencies when building from a git clone.
We do this by converting the full dependency (of the .1 file on
the binary we run with --help) into a dependency on the .c file.
* Makefile.am (do-not-require-help2man): New rule.
(dist-hook): depend on it.
---
 Makefile.am | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index 4999ca1..384b9e9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -92,11 +92,29 @@ BUILT_SOURCES = .version
 .version:
        $(AM_V_GEN)echo $(VERSION) > $@-t && mv $@-t $@

+# In general, we run help2man to build a man page from the binary's --help
+# output, but when building from a just-unpacked distribution tarball, we
+# must not do that, since help2man uses perl.  We don't want to depend on
+# perl in that case.  In general, the .1 file does indeed depend on the
+# binary.  I.e., for cat, we have this Makefile dependency:
+#   man/cat.1: src/cat
+# That means that once we build src/cat, we would trigger the .x.1
+# rule which runs help2man.  The trick is simply to change the RHS to
+# "src/cat.c" in the $(distdir) that we're about to tar and compress.
+# Also handle the three exceptions corresponding to the three binaries
+# for which there is no like-named .c file: dir, vdir, ginstall.
+.PHONY: do-not-require-help2man
+do-not-require-help2man:
+       perl -pi -e 's,^(man/.+?\.1:\s*src/.+?)$$,$$1.c,;'              \
+           -e  's,^(man/.+?\.1:\s*src)/ginstall\.c$$,$$1/install.c,;'  \
+           -e  's,^(man/.+?\.1:\s*src)/v?dir\.c$$,$$1/ls.c,;'          \
+          $(distdir)/Makefile.in
+
 # Arrange so that .tarball-version appears only in the distribution
 # tarball, and never in a checked-out repository.
 # The perl substitution is to change some key uses of "rm" to "/bin/rm".
 # See the rm_subst comment for details.
-dist-hook: gen-ChangeLog
+dist-hook: gen-ChangeLog do-not-require-help2man
        $(AM_V_GEN)echo $(VERSION) > $(distdir)/.tarball-version
        $(AM_V_at)perl -pi -e '$(rm_subst)' $(distdir)/Makefile.in

--
1.7.12.289.g0ce9864