[bug#70380] [PATCH v3 1/4] maint: Cater for running `make dist' from tarball.

[Janneke Nieuwenhuizen]

* Makefile.am (in_git_p): New variable.  Use it 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 | 61 +++++++++++++++++++++++++++++++----------------------
 1 file changed, 36 insertions(+), 25 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 147767ece4..39cf4b4b17 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -953,9 +953,24 @@ 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.  Indented to get past Automake.
+in_git_p = $(shell test -e .git && echo true)
+ ifeq ($(in_git_p),true)
+
+# 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.
+# PACKAGE_VERSION against HEAD.
  ifeq ($(MAKECMDGOALS),dist)
  git_version = $(shell build-aux/git-version-gen .tarball-version)
  ifneq ($(PACKAGE_VERSION),$(git_version))
@@ -967,20 +982,18 @@ 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-hook: gen-ChangeLog gen-AUTHORS gen-tarball-version
+dist: doc-pot-update
+$(warning Not using Git, tarball will likely be irreproducible!)
+
+ 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
@@ -992,27 +1005,25 @@ $(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