subprojects.md: document --wrap-mode
Closes
@@ -72,6 +72,35 @@ in the top level `subprojects` directory. Recursive use of subprojects
is not allowed, though, so you can't have subproject `a` that uses
subproject `b` and have `b` also use `a`.
+# Command-line options
+
+The usage of subprojects can be controlled by users and distros with
+the following command-line options:
+
+* **--wrap-mode=nodownload**
+
+ Meson will not use the network to download any subprojects or
+ fetch any wrap information. Only pre-existing sources will be used.
+ This is useful (mostly for distros) when you want to only use the
+ sources provided by a software release, and want to manually handle
+ or provide missing dependencies.
+
+* **--wrap-mode=nofallback**
+
+ Meson will not use subproject fallbacks for any dependency
+ declarations in the build files, and will only look for them in the
+ system. Note that this does not apply to unconditional subproject()
+ calls, and those are meant to be used for sources that cannot be
+ provided by the system, such as copylibs.
+
+* **--wrap-mode=forcefallback**
+
+ Meson will not look at the system for any dependencies which have
+ subproject fallbacks available, and will *only* use subprojects for
+ them. This is useful when you want to test your fallback setup, or
+ want to specifically build against the library sources provided by
+ your subprojects.
+
# Obtaining subprojects
Meson ships with a dependency system to automatically obtain
