ui-snapshot: add support for zstd compression

This patch adds support for zstd [0] compressed snapshots (*.tar.zst).
We enable multiple working threads (-T0), but keep default compression
level. The latter can be influenced by environment variable.

[0] https://www.zstd.net/

Signed-off-by: Christian Hesse <mail@eworm.de>

1 files changed, 6 insertions, 3 deletions

diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index 4ad3e64..33a6a8c 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -407,9 +407,12 @@ side-by-side-diffs::
 snapshots::
         Text which specifies the default set of snapshot formats that cgit
         generates links for. The value is a space-separated list of zero or
-        more of the values "tar", "tar.gz", "tar.bz2", "tar.xz", "tar.lz" and
-        "zip". The special value "all" enables all snapshot formats.
-        Default value: none.
+        more of the values "tar", "tar.gz", "tar.bz2", "tar.lz", "tar.xz",
+        "tar.zst" and "zip". The special value "all" enables all snapshot
+        formats. Default value: none.
+        All compressors use default settings. Some settings can be influenced
+        with environment variables, for example set ZSTD_CLEVEL=10 in web
+        server environment for higher (but slower) zstd compression.
 
 source-filter::
         Specifies a command which will be invoked to format plaintext blobs