Add help for meson subprojects to the man page.
The added help text was derived from the output of the meson help
command much like the markdown online help is derived.
diff --git a/man/meson.1 b/man/meson.1
index 15b2b93..f7a342b 100644
--- a/man/meson.1
+++ b/man/meson.1
@@ -363,6 +363,49 @@
\fBstatus\fR
show installed and available versions of currently used subprojects
+.SH The subprojects command
+
+.B meson subprojects
+is used to manage subprojects.
+
+.B meson subprojects [
+.I options
+.B ] [
+.I command
+.B ]
+
+.SS "options:"
+.TP
+\fB\-h, \-\-help\fR
+show this help message and exit
+
+.SS "commands:"
+.TP
+\fBupdate\fR
+Update all subprojects from wrap files
+
+.TP
+\fBcheckout\fR
+Checkout a branch (git only)
+
+.TP
+\fBdownload\fR
+Ensure subprojects are fetched, even if not in use. Already downloaded
+subprojects are not modified. This can be used to pre-fetch all
+subprojects and avoid downloads during configure.
+
+.TP
+\fBforeach\fR
+Execute a command in each subproject directory.
+
+.TP
+\fBpurge\fR
+Remove all wrap-based subproject artifacts
+
+.TP
+\fBpackagefiles\fR
+Manage the packagefiles overlay
+
.SH EXIT STATUS
.TP
