wimlib-imagex, wimlib: Optimize appending new image as update of existing

[wimlib] / doc / imagex-capture.1.in

diff --git a/doc/imagex-capture.1.in b/doc/imagex-capture.1.in
index 14522e7c9e20925c0a326b863c7cffa1fae7860a..e12c8bfee252daba9cdc40b66aeb63a7612d6228 100644 (file)
--- a/doc/imagex-capture.1.in
+++ b/doc/imagex-capture.1.in
@@ -393,6 +393,22 @@ Ensure the resulting WIM is in the normal, non-pipable WIM format.  This is the
 default for \fB@IMAGEX_PROGNAME@ capture\fR, except when writing to standard
 output (\fIWIMFILE\fR specified as "-"), and also for \fB@IMAGEX_PROGNAME@
 append\fR, except when appending to a WIM that is already pipable.
+.TP
+\fB--delta-from\fR=\fIIMAGE\fR
+Only for \fB@IMAGEX_PROGNAME@ append\fR: declares that the new image being added
+from \fISOURCE\fR is mostly the same as the existing image \fIIMAGE\fR in
+\fIWIMFILE\fR, but captured at a later point in time, possibly with some
+modifications in the intervening time.  This is designed to be used in
+incremental backups of the same filesystem or directory tree.  \fIIMAGE\fR can
+be a 1-based index or name of an existing image in \fIWIMFILE\fR.  It can also
+be a negative integer to index backwards into the images (e.g.  -1 means the
+last existing image).
+.IP ""
+When this option is provided, the append of the new image will be optimized by
+not reading files that, based on metadata such as timestamps, appear not to have
+been modified since they were archived in the existing \fIIMAGE\fR.  Barring
+manipulation of timestamps, this option only affects performance and does not
+change the resulting WIM file.
 .SH NOTES
 \fB@IMAGEX_PROGNAME@ append\fR does not support appending an image to a split WIM.
 .PP