launch: Allow default attach-method to be set in environment or configure.

You can now choose the default attach method in two ways:

(1) Set the LIBGUESTFS_ATTACH_METHOD environment variable.

(2)  ./configure --with-default-attach-method=appliance|libvirt|...

Note that (1) overrides (2).

1 files changed, 29 insertions, 3 deletions

diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index 74f76bb4..180fce4e 100644
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -1567,14 +1567,18 @@ Please read L<guestfs(3)/INSPECTION> for more details." };
     shortdesc = "set the attach method";
     longdesc = "\
 Set the method that libguestfs uses to connect to the back end
-guestfsd daemon.  Possible methods are:
+guestfsd daemon.
+
+Possible attach methods are:
 
 =over 4
 
 =item C<appliance>
 
-Launch an appliance and connect to it.  This is the ordinary method
-and the default.
+Launch an appliance and connect to it.
+
+This is the ordinary method and normally the default, but see the
+note below.
 
 =item C<libvirt>
 
@@ -1591,6 +1595,28 @@ This method lets you connect to an existing daemon or (using
 virtio-serial) to a live guest.  For more information, see
 L<guestfs(3)/ATTACHING TO RUNNING DAEMONS>.
 
+=back
+
+C<appliance> is usually the default attach method.  However since
+libguestfs E<ge> 1.19.24 it has been possible to change the default
+in two ways:
+
+=over 4
+
+=item Setting LIBGUESTFS_ATTACH_METHOD
+
+Users can set this environment variable to change the default.
+
+=item Configuring the default attach method when building libguestfs
+
+Distributors can override the default when libguestfs is built
+(using C<./configure --with-default-attach-method=...>).
+
+To find out if libguestfs was compiled with a different default
+attach method, do:
+
+ guestfish get-attach-method
+
 =back" };
 
   { defaults with