moved helpers separately

doc/CONTRIBUTING.md

@@ -120,7 +120,7 @@ brew install shellcheck
 - Use `getopt` (not `getopts`) for option parsing — it handles long options and
   `--` correctly.
   Rebuild the arguments from its output with the `_getopt_split` helper
-  (`profile.d/args.sh`), never with `eval set --` or `xargs`:
+  (`helpers/common.sh`), never with `eval set --` or `xargs`:
 
   ```bash
   PARSED=$(getopt -o hv --long help,verbose -n 'mycmd' -- "$@") || return 1
@@ -153,6 +153,29 @@ export -f my_function
 
 Add the `load_conf` call near the top after any variable declarations.
 
+### Helpers
+
+Internal functions (prefixed with `_`) do not belong to the module file; they
+live in the `helpers/` directory:
+
+- `helpers/common.sh`: helpers used by several modules (`_getopt_split`,
+  `_trap_restore`, `_is_uint`, `_profile_load_helpers`). It is loaded by
+  `profile.sh` before any module. Put a helper there as soon as a second module
+  needs it, instead of copying it.
+- `helpers/<module name>.sh`: helpers private to `profile.d/<module name>.sh`
+  (for instance `helpers/rain.sh` for `profile.d/rain.sh`). The file is
+  optional; the module loads it with the two lines below, which also load
+  `common.sh` when the module is sourced alone:
+
+  ```bash
+  declare -F _profile_load_helpers >/dev/null || . "$(dirname -- "${BASH_SOURCE[0]}")/../helpers/common.sh"
+  _profile_load_helpers "${BASH_SOURCE[0]}"
+  ```
+
+Helper files use the same copyright block as the modules and are only
+definitions (no side effect besides the variables the helpers need).
+Document each helper with a comment (purpose, `Usage:` line).
+
 ---
 
 ## 7. Configuration keys
@@ -176,7 +199,7 @@ See the existing themes and `README.md §4.4` for the allowed syntax.
 ## 9. Running shellcheck
 
 ```bash
-shellcheck -x profile.sh profile.d/*.sh
+shellcheck -x profile.sh profile.d/*.sh helpers/*.sh
 ```
 
 All warnings must be resolved before a patch will be accepted. Accepted