+# Overlay a separate directory directly on the root of the WIM image.
+# This is only legal if there are no conflicting files.
+/data/stuff /
+.RE
+.RE
+.fi
+.IP ""
+Subdirectories in the WIM are created as needed. Multiple source directories
+may share the same target, which implies an overlay; however, an error is issued
+if the same file appears in different overlays to the same directory.
+.IP ""
+File paths containing whitespace may be quoted with either single quotes or
+double quotes. Quotes may not be escaped.
+.IP ""
+Lines consisting only of whitespace and lines beginning with '#' preceded by
+optional whitespace are ignored.
+.IP ""
+As a special case, if \fISOURCE\fR is "-", the source list is read from standard
+input rather than an external file.
+.IP ""
+The NTFS volume capture mode on UNIX-like systems cannot be used with
+\fB--source-list\fR, as only capturing a full NTFS volume is supported.
+.TP
+\fB--pipable\fR
+Create a "pipable" WIM, which can be applied fully sequentially, including from
+a pipe. An image in the resulting WIM can be applied with \fB@IMAGEX_PROGNAME@
+apply\fR, either normally by specifying the WIM file name, or with
+\fB@IMAGEX_PROGNAME@ apply -\fR to read the WIM from standard input. See
+\fB@IMAGEX_PROGNAME@ apply\fR(1) for more details.
+.IP ""
+For append operations, this option will result in a full rebuild of the WIM to
+make it pipable. For capture operations, the captured WIM is simply created as
+pipable. Beware that the more images you add to a pipable WIM, the less
+efficient piping it will be, since more unneeded data will be sent through the
+pipe.
+.IP ""
+When wimlib creates a pipable WIM, it carefully re-arranges the components of
+the WIM so that they can be read sequentially and also makes several other
+modifications. As a result, these "pipable" WIMs are \fInot compatible with
+Microsoft's software\fR, so keep this in mind if you're going to use them. If
+desired, you can use \fB@IMAGEX_PROGNAME@ optimize --not-pipable\fR to re-write
+a pipable WIM as a regular WIM. (\fB@IMAGEX_PROGNAME@ export\fR also provides
+the capability to export images from a pipable WIM into a non-pipable WIM, or
+vice versa.)
+.IP ""
+For the most part, wimlib operates on pipable WIMs transparently. You can
+modify them, add or delete images, export images, and even create split pipable
+WIMs. The main disadvantages are that appending is (currently) less efficient
+(\fB--rebuild\fR is always implied), and also they aren't compatible with
+Microsoft's software.
+.IP ""
+\fB@IMAGEX_PROGNAME@ capture\fR and \fB@IMAGEX_PROGNAME@ append\fR can both
+write a pipable WIM directly to standard output; this is done automatically if
+\fIWIMFILE\fR is specified as "-". (In that case, \fB--pipable\fR is assumed.)
+.TP
+\fB--not-pipable\fR
+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.
+.SH NOTES
+\fB@IMAGEX_PROGNAME@ append\fR does not support appending an image to a split WIM.
+.PP
+It is safe to abort an \fB@IMAGEX_PROGNAME@ append\fR command partway through;
+however, after doing this, it is recommended to run \fB@IMAGEX_PROGNAME@
+optimize\fR to remove any data that was appended to the physical WIM file but
+not yet incorporated into the structure of the WIM, unless the WIM was being
+fully rebuilt (e.g. with \fB--rebuild\fR), in which case you should delete the
+temporary file left over.
+.PP
+\fB@IMAGEX_PROGNAME@\fR creates WIMs compatible with Microsoft's software
+(imagex.exe, Dism.exe, wimgapi.dll), with some caveats:
+.IP \[bu] 4
+With \fB@IMAGEX_PROGNAME@\fR on UNIX-like systems, it is possible to create a
+WIM image containing files with names differing only in case, or files with
+names containing the characters ':', '*', '?', '"', '<', '>', '|', or '\\',
+which are valid on POSIX-compliant filesystems but not Windows. Be warned that
+such files will not be extracted by default by the Windows version of
+\fB@IMAGEX_PROGNAME@\fR, and (even worse) Microsoft's ImageX can be confused by
+such names and quit extracting the image partway through. (It perhaps is worth
+pointing out that Windows' own default filesystem, NTFS, supports these
+characters, although Windows does not!)
+.IP \[bu]
+WIMs captured with \fB--unix-data\fR should be assumed to be incompatible with
+Microsoft's software.
+.IP \[bu]
+Pipable WIMs are incompatible with Microsoft's software. Pipable WIMs are
+created only if \fIWIMFILE\fR was specified as "-" (standard output) or if
+the \fB--pipable\fR flag was specified.