Update doc

README.md

@@ -177,13 +177,31 @@ Configuration
            format.
 
        embedded
-           A list of files paths to include in the installation directory.
-           Each element in this list should be a list of two elements: the
-           first being the destination basename (the name of the file in
-           the installation directory), and the second being the path to the
-           directory itself. For example: ["file.txt" "path/to/file"].
-           Relative paths are resolved by searching files in current
-           directory.
+           A list of files or directories paths to include in the installation
+           directory. There are 3 different ways to specify the paths, each of
+           them implies its own installation place in the target directory:
+           
+           First way to install files is by giving a list of two elements: the
+           first being the destination basename (the name of the file in the
+           installation directory), and the second being the path to the file
+           itself. For example: ["file.txt" "path/to/file"]. 
+           
+           The second way is to include any file/directory under opam prefix. 
+           In this case, variables like %{share}% or %{lib}% could be very usefull. 
+           You should just give a list with one string that represents path which
+           prefix is the same with your current switch prefix. For example,
+           ["/absolute-path-to-your-prefix/lib/odoc/odoc.cmi"] or just
+           ["/%{odoc:lib}%/odoc.cmi"]. Those files would be installed in the
+           directory "opam" at the root of installation directory conserving
+           entire path (it would be INSTALLDIR/opam/lib/odoc/odoc.cmi for
+           previous example). 
+           
+           The last way to specify path is very similar with previous, but it 
+           takes into account only external to opam files. The paths to thoses 
+           files should be relative and implicit. For example, ["dir1/dir2/file.txt"]. 
+           The file (or directory) will be installed in "external" directory under 
+           the root of target installation directory the same way as for opam files 
+           (it would be INSTALLDIR/external/dir1/dir2/file.txt for previous example).
 
        envvar
            A list of environment variables to set/unset in the Windows

src/opamWixMain.ml

@@ -668,9 +668,21 @@ let create_bundle cli =
     `I ("$(i,binary-path, binary)","These are the same as their respective arguments.");
     `I ("$(i,wix_version)","The version to use to generate the MSI, in a dot separated number format.");
     `I ("$(i,embedded)", "A list of files or directories paths to include in the installation directory. \
-    Each element in this list should be a list of two elements: the first being the destination \
+    There are 3 different ways to specify the paths, each of them implies its own installation place in \
+    the target directory: \
+    First way to install files is by giving a list of two elements: the first being the destination \
     basename (the name of the file in the installation directory), and the second being the \
-    path to the directory itself. For example: $(i,[\"file.txt\" \"path/to/file\"]).");
+    path to the file itself. For example: $(b,[\"file.txt\" \"path/to/file\"]). \
+    The second way is to include any file/directory under opam prefix. In this case, variables like \
+    $(i,%{share}%) or $(i,%{lib}%) could be very usefull. You should just give a list with one string that \
+    represents path which prefix is the same with your current switch prefix. For example, 
+    $(b,[\"/absolute-path-to-your-prefix/lib/odoc/odoc.cmi\"]) or just $(b,[\"/%{odoc:lib}%/odoc.cmi\"]). \
+    Those files would be installed in the directory \"opam\" at the root of installation directory conserving
+    entire path (it would be $(b,INSTALLDIR/opam/lib/odoc/odoc.cmi) for previous example). \
+    The last way to specify path is very similar with previous, but it takes into account only external to opam files. \
+    The paths to thoses files should be relative and implicit. For example, $(b,[\"dir1/dir2/file.txt\"]).
+    The file (or directory) will be installed in \"external\" directory under the root of target installation directory \
+    the same way as for opam files (it would be $(b,INSTALLDIR/external/dir1/dir2/file.txt) for previous example).");
     `I ("$(i,envvar)", "A list of environment variables to set/unset in the Windows Terminal during \
     install/uninstall. Each element in this list should be a list of two elements: the name and the \
     value of the variable. Basenames defined with $(b,embedded) field could be used as variables, to reference \