tar_filter: recognize .tar.zst as zstd (backport) (#7095)

tar_filter: recognize .tar.zst as zstd

Backported from #7093

src/borg/archiver.py

@@ -3933,7 +3933,7 @@ class Archiver:
         - .tar.gz or .tgz: gzip
         - .tar.bz2 or .tbz: bzip2
         - .tar.xz or .txz: xz
-        - .tar.zstd: zstd
+        - .tar.zstd or .tar.zst: zstd
         - .tar.lz4: lz4
 
         Alternatively, a ``--tar-filter`` program may be explicitly specified. It should
@@ -4876,7 +4876,7 @@ class Archiver:
         - .tar.gz or .tgz: gzip -d
         - .tar.bz2 or .tbz: bzip2 -d
         - .tar.xz or .txz: xz -d
-        - .tar.zstd: zstd -d
+        - .tar.zstd or .tar.zst: zstd -d
         - .tar.lz4: lz4 -d
 
         Alternatively, a --tar-filter program may be explicitly specified. It should

src/borg/helpers/misc.py

@@ -260,7 +260,7 @@ def get_tar_filter(fname, decompress):
         filter = 'xz -d' if decompress else 'xz'
     elif fname.endswith(('.tar.lz4', )):
         filter = 'lz4 -d' if decompress else 'lz4'
-    elif fname.endswith(('.tar.zstd', )):
+    elif fname.endswith(('.tar.zstd', '.tar.zst')):
         filter = 'zstd -d' if decompress else 'zstd'
     else:
         filter = None