Update tar2sqfs/sqfs2tar documentation

Modify the man pages and help texts to mention compression support, make
the help option display a list of supported compressors.

Also clarify the squashfs compressor list in the help text to state that
the list shows block compressors supported for SquashFS compression.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 18 insertions, 11 deletions

diff --git a/bin/sqfs2tar/options.c b/bin/sqfs2tar/options.c
index 356913a..a84fcd4 100644
--- a/bin/sqfs2tar/options.c
+++ b/bin/sqfs2tar/options.c
@@ -62,13 +62,7 @@ static const char *usagestr =
 "  --help, -h                Print help text and exit.\n"
 "  --version, -V             Print version information and exit.\n"
 "\n"
-"Examples:\n"
-"\n"
-"\tsqfs2tar rootfs.sqfs > rootfs.tar\n"
-"\tsqfs2tar rootfs.sqfs | gzip > rootfs.tar.gz\n"
-"\tsqfs2tar rootfs.sqfs | xz > rootfs.tar.xz\n"
-"\n"
-"Available compressors:\n";
+"Supported tar compression formats:\n";
 
 bool dont_skip = false;
 bool keep_as_dir = false;
diff --git a/bin/sqfs2tar/sqfs2tar.1 b/bin/sqfs2tar/sqfs2tar.1
index 0fc69f6..be79312 100644
--- a/bin/sqfs2tar/sqfs2tar.1
+++ b/bin/sqfs2tar/sqfs2tar.1
@@ -11,6 +11,13 @@ archives. The resulting archive is written to stdout.
 .PP
 Possible options:
 .TP
+\fB\-\-compressor\fR, \fB\-c\fR <name>
+By default the result is a raw, uncompressed tar ball. Using this option
+it is possible to select a stream compression format (such as \fBgzip\fR,
+\fBxz\fR, \fBzstd\fR or \fBbzip2\fR) to use for the output archive.
+
+Run \fBsqfs2tar \-\-help\fR to get a list of all available compressors.
+.TP
 \fB\-\-root\-becomes\fR, \fB\-r\fR <dir>
 Prefix all paths in the tarball with the given directory name and add an
 entry for this directory that receives all meta data (permissions, ownership,
@@ -69,18 +76,24 @@ Since the tar format contains a sequence of files with absolute names, it has
 no direct concept of a tree or an unnamed root node. Consequently, meta data
 from the SquashFS root inode is lost, unless the \fB\-\-root\-becomes\fR option
 is used.
+
+The output archive can optionally be compressed. Default settings are used for
+the supported compressors and there is currently no intention to expose finer
+grained control over them. To set custom compressor flags, create an
+uncompressed archive and pipe it into a dedicated compressor process.
+
 .SH EXAMPLES
 Turn a SquashFS image into a tar archive:
 .IP
 sqfs2tar rootfs.sqfs > rootfs.tar
 .TP
-Turn a SquashFS image into a gzip'ed tar archive:
+Creating a compressed archive with gzip headers:
 .IP
-sqfs2tar rootfs.sqfs | gzip > rootfs.tar.gz
+sqfs2tar --compressor gzip rootfs.sqfs > rootfs.tar.gz
 .TP
-Turn a SquashFS image into an LZMA2 compressed tar archive:
+Compressing the output archive, but using custom compressor flags:
 .IP
-sqfs2tar rootfs.sqfs | xz > rootfs.tar.xz
+sqfs2tar rootfs.sqfs | xz -9e > rootfs.tar.xz
 .SH SEE ALSO
 rdsquashfs(1), tar2sqfs(1)
 .SH AUTHOR