Add support for treefmt (#280)

This formatter is formatting via
[treefmt](https://numtide.github.io/treefmt). This is useful if the
project is configuring formatters for the project and you don't have to
replicate this logic within Emacs, but instead utilize treefmt directly.

To do that you can set the `apheleia-formatter` to `treefmt` within the
projects `.dir-locals.el`.

I noticed there are tests for this, since treefmt could technically
format anything, I went with treefmt formatting rust code. It also
relies on having a `treefmt.toml` in the project folder, so had to add
that as well in the tests.

CHANGELOG.md

@@ -32,6 +32,7 @@ The format is based on [Keep a Changelog].
   clojurescript, edn files. ([#271])
 * Stylua is used now in `lua-ts-mode` as well as just `lua-mode`, by
   default ([#275]).
+* [`treefmt`](https://numtide.github.io/treefmt) for project configured formatters ([#280]).
 
 ### Bugs fixed
 * Apheleia sometimes failed to determine indent level from Emacs

apheleia-formatters.el

@@ -185,6 +185,7 @@
     (stylua . ("stylua" "-"))
     (rustfmt . ("rustfmt" "--quiet" "--emit" "stdout"))
     (terraform . ("terraform" "fmt" "-"))
+    (treefmt . ("treefmt" "--stdin" filepath))
     (xmllint . ("xmllint" "--format" "-"))
     (yapf . ("yapf"))
     (yq-csv . ("yq" "--prettyPrint" "--no-colors"

test/formatters/installers/treefmt.bash

@@ -0,0 +1,11 @@
+ver="$(latest_release numtide/treefmt)"
+
+wget "https://github.com/numtide/treefmt/releases/download/${ver}/treefmt-x86_64-unknown-linux-gnu.tar.gz" -O - | tar -C /usr/local/bin -xz
+chmod +x /usr/local/bin/treefmt
+
+apt-get install -y rustfmt
+cat <<EOT >> /tmp/treefmt.toml
+[formatter.rust]
+command = "rustfmt"
+includes = ["*.rs"]
+EOT

test/formatters/samplecode/treefmt/in.rs

@@ -0,0 +1,12 @@
+fn foo() {
+    println!("a");
+}
+
+
+
+fn bar() {
+    println!("b");
+
+
+    println!("c");
+}

test/formatters/samplecode/treefmt/out.rs

@@ -0,0 +1,9 @@
+fn foo() {
+    println!("a");
+}
+
+fn bar() {
+    println!("b");
+
+    println!("c");
+}