[bug#70380] [PATCH v4 3/6] maint: Cater for running `make dist' from tarball.

[Janneke Nieuwenhuizen <janneke@gnu.org>]

* Makefile.am: Use in_git_p conditional to disable Autotools' cache
consistency assert and removal when bulding from tarball.
(dist): Depend on doc-pot-update again when building from tarball.
(dist-hook): Remove dependencies on gen-ChangeLog and gen-AUTHORS when
building from tarball.
(gen-ChangeLog, gen-AUTHORS): Remove guarding for building from tarball.
Use set -e to avoid silently failing.
(gen-tarball-version): Use $(SOURCE_DATE_EPOCH) instead of re-generating it
using git; this also works running from a tarball.

Change-Id: I9ebdd28a70837f6a4db610c4816bb283d176e2d9
---
 Makefile.am | 60 ++++++++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 24 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index ca3fa0a693..af08bc546f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -955,6 +955,20 @@ guix-binary.%.tar.xz:
 	  guix` ;					\
 	cp "$$tarball" "$@.tmp" ; mv "$@.tmp" "$@"
 
+# The `dist' target has other dependencies when building from Git
+# to assert and achieve reproducibility.
+if in_git_p
+
+# The dependency on dist-doc-pot-update is to clean possibly stale doc and po
+# files and only then generate the .pot files, which are not checked in.
+dist: dist-doc-pot-update
+dist-doc-pot-update: auto-clean
+	$(MAKE) guile$(EXEEXT)
+	$(MAKE) -C po/guix all
+	$(MAKE) -C po/packages all
+	$(MAKE) doc-pot-update
+
+dist-hook: gen-ChangeLog gen-AUTHORS
 
 # Assert that Autotools cache is up to date with Git, by checking
 # PACKAGE_VERSION against HEAD.  Indented to get past Automake.
@@ -969,20 +983,20 @@ guix-binary.%.tar.xz:
  $(error Cannot create reproducible tarball)
  else
  $(warning Tarball will be irreproducible; distdir will not get removed!)
- endif
- endif
- endif
+ endif # !GUIX_ALLOW_IRREPRODUCIBLE_TARBALL
+ endif # PACKAGE_VERSION != git_version
+ endif # MAKECMDGOALS dist
 
-# The dependency on dist-doc-pot-update is to clean possibly stale doc and po
-# files and only then generate the .pot files, which are not checked in.
-dist: dist-doc-pot-update
-dist-doc-pot-update: auto-clean
-	$(MAKE) guile$(EXEEXT)
-	$(MAKE) -C po/guix all
-	$(MAKE) -C po/packages all
-	$(MAKE) doc-pot-update
+else # !in_git_p
+
+dist: doc-pot-update
 
-dist-hook: gen-ChangeLog gen-AUTHORS gen-tarball-version
+ ifeq ($(MAKECMDGOALS),dist)
+$(warning Not using Git, tarball will likely be irreproducible!)
+ endif # MAKECMDGOALS dist
+endif # !in_git_p
+
+dist-hook: gen-tarball-version
 dist-hook: assert-no-store-file-names
 
 distcheck-hook: assert-binaries-available assert-final-inputs-self-contained
@@ -994,27 +1008,25 @@ $(top_srcdir)/.version: config.status
 
 gen-tarball-version:
 	echo $(VERSION) > "$(distdir)/.tarball-version"
-	git show HEAD --format=%ct --no-patch > $(distdir)/.tarball-timestamp
+	echo $(SOURCE_DATE_EPOCH) > $(distdir)/.tarball-timestamp
 
 gen-ChangeLog:
-	$(AM_V_GEN)if test -e .git; then		\
-	  export LC_ALL=en_US.UTF-8;			\
-	  export TZ=UTC0;				\
-	  $(top_srcdir)/build-aux/gitlog-to-changelog	\
-	    > $(distdir)/ChangeLog.tmp;			\
-	  rm -f $(distdir)/ChangeLog;			\
-	  mv $(distdir)/ChangeLog.tmp $(distdir)/ChangeLog;	\
-	fi
+	$(AM_V_GEN)set -e;					\
+	  export LC_ALL=en_US.UTF-8;				\
+	  export TZ=UTC0;					\
+	  $(top_srcdir)/build-aux/gitlog-to-changelog		\
+	    > $(distdir)/ChangeLog.tmp;				\
+	  rm -f $(distdir)/ChangeLog;				\
+	  mv $(distdir)/ChangeLog.tmp $(distdir)/ChangeLog;
 
 gen-AUTHORS:
-	$(AM_V_GEN)if test -e .git; then			\
+	$(AM_V_GEN)set -e;					\
 	  rm -f "$(distdir)/AUTHORS";				\
 	  export LC_ALL=en_US.UTF-8;				\
 	  export TZ=UTC0;					\
 	  $(top_builddir)/pre-inst-env "$(GUILE)"		\
 	    "$(top_srcdir)/build-aux/generate-authors.scm"	\
-	    "$(top_srcdir)" "$(distdir)/AUTHORS";		\
-	fi
+	    "$(top_srcdir)" "$(distdir)/AUTHORS";
 
 # Like 'dist', but regenerate 'configure' so we get an up-to-date
 # 'PACKAGE_VERSION' string.  (In Gnulib, 'GNUmakefile' has a special trick to
-- 
2.41.0