Delete change detector, just build the whole font always. Shuffle thi…

…ngs as a result.

README.md

@@ -6,7 +6,7 @@ Where in we pursue oxidizing [fontmake](https://github.com/googlefonts/fontmake)
 For context around where fontmake came from see
 [Mr B goes to Vartown](https://github.com/googlefonts/oxidize/blob/main/text/2023-10-18-mrb-goes-to-vartown.md).
 
-Converts source to IR, and then IR to font binary. Aims to be safe, incremental, and fast.
+Converts source to IR, and then IR to font binary. Aims to be safe and fast.
 
 References
 
@@ -47,14 +47,13 @@ Install the latest version of Rust, https://www.rust-lang.org/tools/install.
 $ cargo run -p fontc -- resources/testdata/wght_var.designspace
 ```
 
-### Emit IR to enable incremental builds
+### Emit IR
 
-If you pass the `--incremental` (or `-i`) option, the IR will be written to disk inside
-the build working directory, so that the next time you run fontc with the same source file
-only what changed will be rebuilt.
+If you pass the `--emit-ir` option, the IR will be written to disk inside
+the build working directory. This can be helpful when troubleshooting.
 
 ```shell
-$ cargo run -p fontc -- --incremental resources/testdata/wght_var.designspace
+$ cargo run -p fontc -- --emit-ir resources/testdata/wght_var.designspace
 $ ls build/
 ```
 

fontc/src/args.rs

@@ -23,9 +23,9 @@ pub struct Args {
     #[arg(short, long)]
     source: Option<PathBuf>,
 
-    /// Whether to write IR to disk. Must be true if you want incremental compilation.
+    /// Whether to write IR to disk.
     #[arg(short, long, default_value = "false")]
-    pub incremental: bool,
+    pub emit_ir: bool,
 
     /// Output file name (default: build/font.ttf)
     #[arg(short, long)]
@@ -109,7 +109,7 @@ impl Args {
     pub fn flags(&self) -> Flags {
         let mut flags = Flags::default();
 
-        flags.set(Flags::EMIT_IR, self.incremental);
+        flags.set(Flags::EMIT_IR, self.emit_ir);
         flags.set(Flags::EMIT_DEBUG, self.emit_debug);
         flags.set(Flags::PREFER_SIMPLE_GLYPHS, self.prefer_simple_glyphs);
         flags.set(Flags::FLATTEN_COMPONENTS, self.flatten_components);
@@ -129,7 +129,7 @@ impl Args {
             glyph_name_filter: None,
             input_source: Some(input_source),
             source: None,
-            incremental: true,
+            emit_ir: false,
             output_file: None,
             emit_debug: false, // they get destroyed by test cleanup
             emit_timing: false,
@@ -152,7 +152,9 @@ impl Args {
         use crate::testdata_dir;
 
         let input_source = testdata_dir().join(source).canonicalize().unwrap();
-        Self::new(build_dir, input_source)
+        let mut result = Self::new(build_dir, input_source);
+        result.emit_ir = true;
+        result
     }
 
     /// The input source to compile.