rescue: Pass $TERM from library into the virt-rescue appliance.

We set it on the kernel command line, then get it out from
there when the rescue appliance boots.

appliance/init

@@ -78,7 +78,7 @@ if ! grep -sq guestfs_rescue=1 /proc/cmdline; then
 fi
 
 # Use appliance in rescue mode, also used by the virt-rescue command.
-TERM=linux ;# XXX library should pass this from library's environment
+eval $(grep -Eo 'TERM=[^[:space:]]+' /proc/cmdline)
 PS1='><rescue> '
 export TERM PS1
 echo

src/guestfs.c

@@ -1257,10 +1257,12 @@ guestfs__launch (guestfs_h *g)
               "%s "             /* (selinux) */
               "%s "             /* (vmchannel) */
               "%s "             /* (verbose) */
+              "TERM=%s "        /* (TERM environment variable) */
               "%s",             /* (append) */
               g->selinux ? "selinux=1 enforcing=0" : "selinux=0",
               vmchannel ? vmchannel : "",
               g->verbose ? "guestfs_verbose=1" : "",
+              getenv ("TERM") ? : "linux",
               g->append ? g->append : "");
 
     add_cmdline (g, "-kernel");