[RFC/PATCH] t0107: support older tar in zstd untar test

[Todd Zullinger]

Yesterday, I wrote:
> Does cgit intend to require GNU tar?  If not, perhaps we should instead
> justify this primarily for compatibility with a wider range of tar
> implementations in addition to supporting older versions of GNU tar?

The more I thought about it, the more I liked that idea.  It
makes it simpler for new compression algorithms to re-use
the tests for the existing algorithms.  We could potentially
even create a helper function to handle each compression algo.

So here's that version in patch form.

-- 8< --
Subject: [PATCH] t0107: support older and/or non-GNU tar

The untar tests for various compression algorithms use shortcut options
from GNU tar to handle decompression.  These options may not be provided
by non-GNU tar nor even by slightly older GNU tar versions which ship on
many systems. 

An example of the latter case is the --zstd option.  This was added in
GNU tar-1.32 (2019-02-23)¹.  This version of tar is not provided by
CentOS/RHEL, in particular.  In Debian, --zstd has been backported to
the tar-1.30 release.

Avoid the requirement on any specific implementations or versions of tar
by piping decompressed output to tar.  This is compatible with older GNU
tar releases as well as tar implementations from other vendors.  (It may
also be a slight benefit that this more closely matches what the
snapshot creation code does.)

¹ Technically, the --zstd option was first released in tar-1.31
  (2019-01-02), but this release was very short-lived and is no longer
  listed on the GNU Tar release page.

Signed-off-by: Todd Zullinger <tmz at pobox.com>
---
 tests/t0107-snapshot.sh | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/t0107-snapshot.sh b/tests/t0107-snapshot.sh
index c164d3e..8ea95ce 100755
--- a/tests/t0107-snapshot.sh
+++ b/tests/t0107-snapshot.sh
@@ -25,7 +25,7 @@ test_expect_success 'verify gzip format' '
 
 test_expect_success 'untar' '
 	rm -rf master &&
-	tar -xzf master.tar.gz
+	gzip -dc master.tar.gz | tar -xf -
 '
 
 test_expect_success 'count files' '
@@ -67,7 +67,7 @@ test_expect_success LZIP 'verify lzip format' '
 
 test_expect_success LZIP 'untar' '
 	rm -rf master &&
-	tar --lzip -xf master.tar.lz
+	lzip -dc master.tar.lz | tar -xf -
 '
 
 test_expect_success LZIP 'count files' '
@@ -109,7 +109,7 @@ test_expect_success XZ 'verify xz format' '
 
 test_expect_success XZ 'untar' '
 	rm -rf master &&
-	tar --xz -xf master.tar.xz
+	xz -dc master.tar.xz | tar -xf -
 '
 
 test_expect_success XZ 'count files' '
@@ -151,7 +151,7 @@ test_expect_success ZSTD 'verify zstd format' '
 
 test_expect_success ZSTD 'untar' '
 	rm -rf master &&
-	tar --zstd -xf master.tar.zst
+	zstd -dc master.tar.zst | tar -xf -
 '
 
 test_expect_success ZSTD 'count files' '

-- 
Todd