rewriter: create {add,rm}_extra_files commands

Add ability to mutate a target's `extra_files` list through the
rewriter.

The logic is copied from sources add/rm, but changes the `extra_files`
kwarg instead of the sources positional argument.
Has additional logic to handle creating the `extra_files` list if it
doesn't exist.

2 files changed, 38 insertions, 1 deletions

diff --git a/docs/markdown/Rewriter.md b/docs/markdown/Rewriter.md
index 018434f..535093b 100644
--- a/docs/markdown/Rewriter.md
+++ b/docs/markdown/Rewriter.md
@@ -77,6 +77,17 @@ and print an error message.
 For more information see the help output of the rewriter target
 command.
 
+### Adding and removing `extra_files`
+
+*Since 0.61.0*
+
+In the same way you can add and remove source files from a target, you can modify a target's
+`extra_files` list:
+
+```bash
+meson rewrite target <target name/id> {add_extra_files/rm_extra_files} [list of extra files]
+```
+
 ### Setting the project version
 
 It is also possible to set kwargs of specific functions with the
@@ -191,7 +202,7 @@ The format for the type `target` is defined as follows:
 {
   "type": "target",
   "target": "target ID/name/assignment variable",
-  "operation": "one of ['src_add', 'src_rm', 'target_rm', 'target_add', 'info']",
+  "operation": "one of ['src_add', 'src_rm', 'target_rm', 'target_add', 'extra_files_add', 'extra_files_rm', 'info']",
   "sources": ["list", "of", "source", "files", "to", "add, remove"],
   "subdir": "subdir where the new target should be added (only has an effect for operation 'tgt_add')",
   "target_type": "function name of the new target -- same as in the CLI (only has an effect for operation 'tgt_add')"
diff --git a/docs/markdown/snippets/rewriter_extra_files.md b/docs/markdown/snippets/rewriter_extra_files.md
new file mode 100644
index 0000000..c46f076
--- /dev/null
+++ b/docs/markdown/snippets/rewriter_extra_files.md
@@ -0,0 +1,26 @@
+## `meson rewrite` can modify `extra_files`
+
+The build script rewriter can now modify targets' `extra_files` lists,
+or create them if absent. It it used in the same way as with rewriting
+source lists:
+
+```bash
+meson rewrite target <target name/id> {add_extra_files/rm_extra_files} [list of extra files]
+```
+
+The rewriter's script mode also supports these actions:
+
+```json
+{
+  "type": "target",
+  "target": "<target name>",
+  "operation": "extra_files_add / extra_files_rm",
+  "sources": ["list", "of", "extra", "files", "to", "add, remove"],
+}
+```
+
+## `meson rewrite target <target> info` outputs *target*'s `extra_files`
+
+Targets' `extra_files` lists are now included in the rewriter's target info dump
+as a list of file paths, in the same way `sources` are. This applies to both
+`meson rewrite` CLI and script mode.