dist: add dist-zstd option

Add support for using the zstd compression algorithm.
Use a default compression setting of -19, and ".zst" as the suffix.

* bin/automake.in (handle_dist): Add zstd to the list of known dist-
suffixes.
(preprocess_file): Map ZSTD to dist-zstd.
* doc/automake.texi: Document the new option.
* lib/Automake/Options.pm (_is_valid_easy_option): Add dist-zstd.
* lib/am/distdir.am (dist-zstd): New rule.
(?ZSTD?DIST_TARGETS): Add definition.
(distcheck): Add a case for *.tar.zst*.
* t/dist-formats.tap: Add tests.
* NEWS: Mention the change.

6 files changed, 40 insertions, 6 deletions

diff --git a/NEWS b/NEWS
index d4f781ea9..bb3fff83f 100644
--- a/NEWS
+++ b/NEWS
@@ -64,6 +64,10 @@
 
 New in ?.?.?:
 
+* New features added
+
+  - add zstd support and the automake option, dist-zstd.
+
 * Miscellaneous changes
 
   - automake no longer requires a @setfilename in each .texi file
diff --git a/bin/automake.in b/bin/automake.in
index 06f4ee9b2..67a7a9578 100644
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -3806,7 +3806,7 @@ sub handle_dist ()
     {
       my $archive_defined = option 'no-dist-gzip' ? 0 : 1;
       $archive_defined ||=
-	grep { option "dist-$_" } qw(shar zip tarZ bzip2 lzip xz);
+	grep { option "dist-$_" } qw(shar zip tarZ bzip2 lzip xz zstd);
       error (option 'no-dist-gzip',
 	     "no-dist-gzip specified but no dist-* specified,\n"
 	     . "at least one archive format must be enabled")
@@ -6788,6 +6788,7 @@ sub preprocess_file
 		 'GZIP'        =>  ! option 'no-dist-gzip',
 		 'SHAR'        => !! option 'dist-shar',
 		 'ZIP'         => !! option 'dist-zip',
+		 'ZSTD'        => !! option 'dist-zstd',
 
 		 'INSTALL-INFO' =>  ! option 'no-installinfo',
 		 'INSTALL-MAN'  =>  ! option 'no-installman',
diff --git a/doc/automake.texi b/doc/automake.texi
index 732aa1303..09374a8aa 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -8750,6 +8750,17 @@ It and the corresponding functionality will be removed altogether
 in Automake 2.0.
 @trindex dist-shar
 
+@vindex ZSTD_OPT
+@vindex ZSTD_CLEVEL
+@item @code{dist-zstd}
+Generate a @samp{zstd} tar archive of the distribution.  By default, this
+rule makes @samp{zstd} use a compression option of @option{-19}.  To
+make it use a different one, set the @env{ZSTD_OPT} environment variable.
+For example, run this command to use the default compression ratio,
+but with a progress indicator: @samp{make dist-zstd ZSTD_OPT=-19v}.
+However, note that for compatibility with zstd itself, you may instead set the @env{ZSTD_CLEVEL} environment variable, in which case, any @env{ZSTD_OPT} setting is ignored.
+@trindex dist-zstd
+
 @end table
 
 The rule @code{dist} (and its historical synonym @code{dist-all})
@@ -10123,6 +10134,12 @@ Hook @code{dist-xz} to @code{dist}.
 Hook @code{dist-zip} to @code{dist}.
 @trindex dist-zip
 
+@item @option{dist-zstd}
+@cindex Option, @option{dist-zstd}
+@opindex dist-zstd
+Hook @code{dist-zstd} to @code{dist}.
+@trindex dist-zstd
+
 @item @option{dist-shar}
 @cindex Option, @option{dist-shar}
 @opindex dist-shar
@@ -10316,8 +10333,8 @@ the source file.  For instance, if the source file is
 These three mutually exclusive options select the tar format to use
 when generating tarballs with @samp{make dist}.  (The tar file created
 is then compressed according to the set of @option{no-dist-gzip},
-@option{dist-bzip2}, @option{dist-lzip}, @option{dist-xz} and
-@option{dist-tarZ} options in use.)
+@option{dist-bzip2}, @option{dist-lzip}, @option{dist-xz},
+@option{dist-zstd} and @option{dist-tarZ} options in use.)
 
 These options must be passed as arguments to @code{AM_INIT_AUTOMAKE}
 (@pxref{Macros}) because they can require additional configure checks.
@@ -13228,4 +13245,4 @@ suite failures, please attach the @file{test-suite.log} file.
 @c  LocalWords:  LTALLOCA MALLOC malloc memcmp strdup alloca libcompat xyz DFOO
 @c  LocalWords:  unprefixed buildable preprocessed DBAZ DDATADIR WARNINGCFLAGS
 @c  LocalWords:  LIBFOOCFLAGS LIBFOOLDFLAGS ftable testSubDir obj LIBTOOLFLAGS
-@c  LocalWords:  barexec Pinard's automatize initialize lzip xz cscope
+@c  LocalWords:  barexec Pinard's automatize initialize lzip xz zstd cscope
diff --git a/lib/Automake/Options.pm b/lib/Automake/Options.pm
index 5a85b753a..7aaad86dd 100644
--- a/lib/Automake/Options.pm
+++ b/lib/Automake/Options.pm
@@ -277,6 +277,7 @@ sub _is_valid_easy_option ($)
     dist-lzip
     dist-xz
     dist-zip
+    dist-zstd
     info-in-builddir
     no-define
     no-dependencies
diff --git a/lib/am/distdir.am b/lib/am/distdir.am
index ec78ca70c..cdd77eb83 100644
--- a/lib/am/distdir.am
+++ b/lib/am/distdir.am
@@ -350,6 +350,12 @@ dist-xz: distdir
 	tardir=$(distdir) && $(am__tar) | XZ_OPT=$${XZ_OPT--e} xz -c >$(distdir).tar.xz
 	$(am__post_remove_distdir)
 
+?ZSTD?DIST_ARCHIVES += $(distdir).tar.zst
+.PHONY: dist-zstd
+dist-zstd: distdir
+	tardir=$(distdir) && $(am__tar) | zstd -c $${ZSTD_CLEVEL-$${ZSTD_OPT--19}} >$(distdir).tar.zst
+	$(am__post_remove_distdir)
+
 ?COMPRESS?DIST_ARCHIVES += $(distdir).tar.Z
 .PHONY: dist-tarZ
 dist-tarZ: distdir
@@ -381,6 +387,7 @@ dist-zip: distdir
 ?BZIP2?DIST_TARGETS += dist-bzip2
 ?GZIP?DIST_TARGETS += dist-gzip
 ?ZIP?DIST_TARGETS += dist-zip
+?ZSTD?DIST_TARGETS += dist-zstd
 ?COMPRESS?DIST_TARGETS += dist-tarZ
 
 endif %?TOPDIR_P%
@@ -438,6 +445,8 @@ distcheck: dist
 	  eval GZIP= gzip $(GZIP_ENV) -dc $(distdir).shar.gz | unshar ;;\
 	*.zip*) \
 	  unzip $(distdir).zip ;;\
+	*.tar.zst*) \
+	  zstd -dc $(distdir).tar.zst | $(am__untar) ;;\
 	esac
 ## Make the new source tree read-only.  Distributions ought to work in
 ## this case.  However, make the top-level directory writable so we
diff --git a/t/dist-formats.tap b/t/dist-formats.tap
index 588b22fe6..3a91160c5 100644
--- a/t/dist-formats.tap
+++ b/t/dist-formats.tap
@@ -20,7 +20,7 @@
 am_create_testdir=empty
 . test-init.sh
 
-plan_ 66
+plan_ 75
 
 # ---------------------------------------------------- #
 #  Common and/or auxiliary subroutines and variables.  #
@@ -60,6 +60,7 @@ setup_vars_for_compression_format ()
       xz) suffix=tar.xz  compressor=xz       ;;
    bzip2) suffix=tar.bz2 compressor=bzip2    ;;
      zip) suffix=zip     compressor=zip      ;;
+    zstd) suffix=tar.zst compressor=zstd     ;;
        *) fatal_ "invalid compression format '$1'";;
   esac
 }
@@ -101,7 +102,7 @@ have_compressor ()
   return 0
 }
 
-all_compression_formats='gzip lzip xz bzip2 zip'
+all_compression_formats='gzip lzip xz bzip2 zip zstd'
 
 all_compressors=$(
   for x in $all_compression_formats; do
@@ -294,6 +295,7 @@ nogzip in am  and  bzip2  in  am
 nogzip in ac  and  xz     in  am
 nogzip in am  and  lzip   in  ac
 nogzip in ac  and  zip    in  ac
+nogzip in ac  and  zstd   in  ac
 
 
 # ----------------------------------------------------------- #