Update README.md: add description, options, related links

README.md

@@ -1,2 +1,47 @@
-# brotli-cli
-brotli CLI tool built as statically-linked binary
+# brotli CLI tool
+
+brotli CLI tool v1.0 for compression (or decompression) files. Compiled from [official sources](https://github.com/google/brotli/tree/master/c/tools) as a static executable for using on some embedded devices. Tested on Alpine Linux 3.6
+
+## OPTIONS
+
+* `-#`:
+    compression level (0-9); bigger values cause denser, but slower compression
+* `-c`, `--stdout`:
+    write on standard output
+* `-d`, `--decompress`:
+    decompress mode
+* `-f`, `--force`:
+    force output file overwrite
+* `-h`, `--help`:
+    display this help and exit
+* `-j`, `--rm`:
+    remove source file(s); `gzip (1)`-like behaviour
+* `-k`, `--keep`:
+    keep source file(s); `zstd (1)`-like behaviour
+* `-n`, `--no-copy-stat`:
+    do not copy source file(s) attributes
+* `-o FILE`, `--output=FILE`
+    output file; valid only if there is a single input entry
+* `-q NUM`, `--quality=NUM`:
+    compression level (0-11); bigger values cause denser, but slower compression
+* `-t`, `--test`:
+    test file integrity mode
+* `-v`, `--verbose`:
+    increase output verbosity
+* `-w NUM`, `--lgwin=NUM`:
+    set LZ77 window size (0, 10-24) (default: 22); window size is
+    `(2**NUM - 16)`; 0 lets compressor decide over the optimal value; bigger
+    windows size improve density; decoder might require up to window size
+    memory to operate
+* `-S SUF`, `--suffix=SUF`:
+    output file suffix (default: `.br`)
+* `-V`, `--version`:
+    display version and exit
+* `-Z`, `--best`:
+    use best compression level (default); same as "`-q 11`"
+
+## Related links
+
+[brotli official repository](https://github.com/google/brotli)
+
+brotli is open-sourced under the [MIT License](https://opensource.org/licenses/MIT).