Pull common methods into shell_utils.sh, which can be included by scripts.

So we can stop copying gettop and others all over the place.

Test: manual
Bug: 260003429
Change-Id: Ic1b5d6bec8726d9253fb33ec588e503d6fc8167a
diff --git a/envsetup.sh b/envsetup.sh
index 4990800..a30f6bd 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -1,3 +1,55 @@
+# Copyright (C) 2022 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# gettop is duplicated here and in shell_utils.mk, because it's difficult
+# to find shell_utils.make without it for all the novel ways this file can be
+# sourced.  Other common functions should only be in one place or the other.
+function _gettop_once
+{
+    local TOPFILE=build/make/core/envsetup.mk
+    if [ -n "$TOP" -a -f "$TOP/$TOPFILE" ] ; then
+        # The following circumlocution ensures we remove symlinks from TOP.
+        (cd "$TOP"; PWD= /bin/pwd)
+    else
+        if [ -f $TOPFILE ] ; then
+            # The following circumlocution (repeated below as well) ensures
+            # that we record the true directory name and not one that is
+            # faked up with symlink names.
+            PWD= /bin/pwd
+        else
+            local HERE=$PWD
+            local T=
+            while [ \( ! \( -f $TOPFILE \) \) -a \( "$PWD" != "/" \) ]; do
+                \cd ..
+                T=`PWD= /bin/pwd -P`
+            done
+            \cd "$HERE"
+            if [ -f "$T/$TOPFILE" ]; then
+                echo "$T"
+            fi
+        fi
+    fi
+}
+T=$(_gettop_once)
+if [ ! "$T" ]; then
+    echo "Couldn't locate the top of the tree. Always source build/envsetup.sh from the root of the tree." >&2
+    return 1
+fi
+IMPORTING_ENVSETUP=true source $T/build/make/shell_utils.sh
+
+
+# Help
 function hmm() {
 cat <<EOF
 
@@ -928,33 +980,6 @@
     destroy_build_var_cache
 }
 
-function gettop
-{
-    local TOPFILE=build/make/core/envsetup.mk
-    if [ -n "$TOP" -a -f "$TOP/$TOPFILE" ] ; then
-        # The following circumlocution ensures we remove symlinks from TOP.
-        (cd "$TOP"; PWD= /bin/pwd)
-    else
-        if [ -f $TOPFILE ] ; then
-            # The following circumlocution (repeated below as well) ensures
-            # that we record the true directory name and not one that is
-            # faked up with symlink names.
-            PWD= /bin/pwd
-        else
-            local HERE=$PWD
-            local T=
-            while [ \( ! \( -f $TOPFILE \) \) -a \( "$PWD" != "/" \) ]; do
-                \cd ..
-                T=`PWD= /bin/pwd -P`
-            done
-            \cd "$HERE"
-            if [ -f "$T/$TOPFILE" ]; then
-                echo "$T"
-            fi
-        fi
-    fi
-}
-
 # TODO: Merge into gettop as part of launching multitree
 function multitree_gettop
 {