ch-run: set default HOME value

bin/ch-run.c

@@ -255,8 +255,12 @@ void fix_environment(struct args *args)
    char *old_value, *new_value;
 
    // $HOME: If --home, set to “/home/$USER”.
-   if (args->c.host_home)
+   if (args->c.host_home) {
       Z_ (setenv("HOME", cat("/home/", username), 1));
+   } else if (path_exists("/root", NULL, true)) {
+      Z_ (setenv("HOME", "/root", 1));
+   } else
+      Z_ (setenv("HOME", "/", 1));
 
    // $PATH: Append /bin if not already present.
    old_value = getenv("PATH");

doc/ch-run.rst

@@ -317,6 +317,8 @@ Environment variables
 :code:`ch-run` leaves environment variables unchanged, i.e. the host
 environment is passed through unaltered, except:
 
+* by default (:code:`--home` not specified), :code:`HOME` is set to
+  :code:`/root`, if it exists, and :code:`/` otherwise.
 * limited tweaks to avoid significant guest breakage;
 * user-set variables via :code:`--set-env`;
 * user-unset variables via :code:`--unset-env`; and

examples/chtest/Build

@@ -125,6 +125,8 @@ chmod 0777 img/maxperms_file
 mkdir img/maxperms_dir
 chmod 1777 img/maxperms_dir
 
+# Get rid of “/root” directory, used for “HOME” test in “ch-run_misc.bats”.
+rmdir "$img"/root
 
 ## Tar it up.
 

test/run/ch-run_misc.bats

@@ -60,17 +60,27 @@ EOF
 }
 
 @test "\$HOME" {
+    [[ $CH_TEST_BUILDER != 'none' ]] || skip 'image builder required'
+    LC_ALL=C
+
     scope quick
     echo "host: $HOME"
     [[ $HOME ]]
     [[ $USER ]]
 
     # default: no change
     # shellcheck disable=SC2016
+    run ch-run "${ch_imgdir}"/quick -- /bin/sh -c 'echo $HOME'
+    echo "$output"
+    [[ $status -eq 0 ]]
+    [[ $output = "/root" ]]
+
+    # default: no “/root”
+    # shellcheck disable=SC2016
     run ch-run "$ch_timg" -- /bin/sh -c 'echo $HOME'
     echo "$output"
     [[ $status -eq 0 ]]
-    [[ $output = "$HOME" ]]
+    [[ $output = "/" ]]
 
     # set $HOME if --home
     # shellcheck disable=SC2016