Adjusted package_module and paths for termux platform

Packages promises only possibly supported back to 3.15.1 due to
need for interpreter attribute on package_module body and no
earlier version available for termux.

Paths added to support the interpreter path for packages.
Also several convenience paths added both for termux and generic unix:
- paths.tmp_path, paths.bin_path, paths.var_path, paths.etc_path

Ticket: CFE-3288
Changelog: Title

Author: craigcomstock

lib/packages.cf

@@ -32,13 +32,20 @@ bundle common package_module_knowledge
     windows::
       "platform_default" string => "msiexec";
 @endif
+
+    termux::
+      "platform_default" string => "apt_get";
 }
 
 body package_module apt_get
 {
     query_installed_ifelapsed => "$(def.package_module_query_installed_ifelapsed)";
     query_updates_ifelapsed => "$(def.package_module_query_updates_ifelapsed)";
     #default_options =>  {};
+@if minimum_version(3.12.2)
+    termux::
+      interpreter => "$(paths.bin_path)/python";
+@endif
 }
 
 body package_module zypper

lib/paths.cf

@@ -1,8 +1,8 @@
 # Paths bundle (used by other bodies)
 
 bundle common paths
-# @brief Defines an array `path` with common paths to standard binaries,
-# and classes for defined and existing paths.
+# @brief Defines an array `path` with common paths to standard binaries and
+# directories as well as classes for defined and existing paths.
 #
 # If the current platform knows that binary XYZ should be present,
 # `_stdlib_has_path_XYZ` is defined. Furthermore, if XYZ is actually present
@@ -25,6 +25,22 @@ bundle common paths
 #        comment => "Alternate array reference style";
 # }
 # ```
+#
+# Additionally several path entries are present to aid in policy sharing between
+# unix systems and Android Termux environments.
+#
+# **Example:**
+#
+# ```cf3
+# bundle agent track_sshd_config
+# {
+#   files:
+#     "$(paths.etc_path)/sshd/sshd_config"
+#       changes => detect_all_change;
+# }
+# ```
+#
+# In case of termux, `paths.etc_path` will be `/data/data/com.termux/files/usr/etc`.
 {
   vars:
 
@@ -570,6 +586,32 @@ bundle common paths
 
       "path[shadow]"       string => "/etc/security/passwd";
 
+    termux::
+      "path[tar]"           string => "/usr/bin/tar";
+      "path[true]"          string => "/usr/bin/true";
+      "path[false]"         string => "/usr/bin/false";
+      "path[cat]"           string => "/usr/bin/cat";
+      "path[sysctl]"        string => "/usr/bin/sysctl";
+      "path[env]"           string => "/usr/bin/env";
+
+      # now, mangle the values by prepending the TERMUX_PREFIX
+      "files_path" string => "/data/data/com.termux/files";
+      "etc_path" string => "$(files_path)/usr/etc";
+      "tmp_path" string => "$(files_path)/usr/tmp";
+      "bin_path" string => "$(files_path)/usr/bin";
+      "var_path" string => "$(files_path)/usr/var";
+      "tmp_paths" slist => getindices("path");
+      "tmp_path[$(tmp_paths)]" string => "$(files_path)$(path[$(tmp_paths)])";
+      "path[$(tmp_paths)]" string => "$(tmp_path[$(tmp_paths)])";
+
+    !(termux|windows)::
+      # reasonable defaults for unix systems to allow for writing
+      # more portable paths between termux and other systems
+      "etc_path" string => "/etc";
+      "tmp_path" string => "/tmp";
+      "bin_path" string => "/bin";
+      "var_path" string => "/var";
+
     any::
 
       "all_paths"     slist => getindices("path");

promises.cf.in

@@ -107,6 +107,8 @@ body common control
           package_inventory => { $(package_module_knowledge.platform_default) };
           package_module => $(package_module_knowledge.platform_default);
 @endif
+    termux::
+          package_module => $(package_module_knowledge.platform_default);
 
     any::
         ignore_missing_bundles => "$(def.control_common_ignore_missing_bundles)";