add zbat wrapper to decompress files automatically

This relies on bsdcat from archive-tools, which supports more formats
than just gzip or, failing that, falls back to gunzip -c with a
warning.

Previously[1], @sharkdp stated that bat would not support compressed
files, but would be open in implementing a wrapper. There was another
implementation proposed elsewhere[2], but it seems overengineered to
me.

[1] #642 (comment)
[2] #237 (comment)

Author: anarcat

Diff for: CHANGELOG.md

@@ -1,6 +1,7 @@
 # unreleased
 
 ## Features
+* Add a `zbat` wrapper script to automatically decompress files before display, see PR #3177 (@anarcat)
 
 ## Bugfixes
 * Fix `BAT_THEME_DARK` and `BAT_THEME_LIGHT` being ignored, see issue #3171 and PR #3168 (@bash)

Diff for: bin/zbat

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+set -e
+set -u
+# shellcheck disable=SC3040
+(set -o pipefail 2> /dev/null) && set -o pipefail
+
+cpath="$1"
+# cpath without suffix
+path="$(echo $cpath | sed 's/\.[^.]*$//')"
+
+( bsdcat "$path" || gunzip -c "$path" ) | batcat --file-name "$path"