diff --git a/.editorconfig b/.editorconfig
deleted file mode 100644
index 54b2e85..0000000
--- a/.editorconfig
+++ /dev/null
@@ -1,29 +0,0 @@
-# Editor configuration, see http://editorconfig.org
-root = true
-
-[*]
-end_of_line = lf
-insert_final_newline = true
-trim_trailing_whitespace = true
-charset = utf-8
-indent_style = space
-indent_size = 2
-
-# Ignore diffs/patches
-[*.{diff,patch}]
-end_of_line = unset
-insert_final_newline = unset
-trim_trailing_whitespace = unset
-indent_size = unset
-
-[*.md]
-max_line_length = off
-trim_trailing_whitespace = false
-
-[tests/cases/**]
-end_of_line = unset
-insert_final_newline = unset
-trim_trailing_whitespace = unset
-charset = unset
-indent_style = unset
-indent_size = unset
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f95a7f..b7f17aa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,9 +17,40 @@ Types of changes
 - Security in case of vulnerabilities.
 -->
 
+## [0.4.0] - 2022-02-21
+
 ### Added
 
-- A text user interface with progress-bars and modern output (requires a TTY).
+- A text user interface with a progress-bar
+  and modern, colorful output (requires a tty).
+
+  When no tty is available
+  or in non-interactive environments like a CI/CD
+  or when piping alejandra to other commands (`$ alejandra 2> file`, `$ alejandra | cat`)
+  the old school program output will be used.
+
+- A `--exclude` option to the CLI.
+
+- Refactors to the codebase. We now comply with `clippy`, a Rust linter.
+
+- A new structure to the codebase and link time optimizations.
+
+  Binaries were reduced in size by 15%
+  with respect to the previous release
+  (even with the added features),
+  performance was improved in the reference machine
+  from 45 seconds to 35 while formatting Nixpkgs on a single core.
+
+### Changed
+
+- The old school program output is now less verbose.
+
+  It prints only the path of files that were changed,
+  and a summary of the number of errors and files changed during formatting.
+
+### Removed
+
+- The `--debug` flag in the CLI.
 
 ## [0.3.1] - 2022-02-20
 
@@ -175,7 +206,8 @@ Types of changes
 
 ---
 
-[unreleased]: https://github.com/kamadorueda/alejandra/compare/0.3.1...HEAD
+[unreleased]: https://github.com/kamadorueda/alejandra/compare/0.4.0...HEAD
+[0.4.0]: https://github.com/kamadorueda/alejandra/compare/0.3.1...0.4.0
 [0.3.1]: https://github.com/kamadorueda/alejandra/compare/0.3.0...0.3.1
 [0.3.0]: https://github.com/kamadorueda/alejandra/compare/0.2.0...0.3.0
 [0.2.0]: https://github.com/kamadorueda/alejandra/compare/0.1.0...0.2.0
diff --git a/Cargo.lock b/Cargo.lock
index c0306d5..22fd70e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,7 +4,7 @@ version = 3
 
 [[package]]
 name = "alejandra_cli"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "alejandra_engine",
  "atty",
@@ -18,7 +18,7 @@ dependencies = [
 
 [[package]]
 name = "alejandra_engine"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "clap",
  "rand",
diff --git a/README.md b/README.md
index 329258e..54f4fa2 100644
--- a/README.md
+++ b/README.md
@@ -109,11 +109,11 @@ You can download a binary for your platform,
 make it executable (`$ chmod +x`)
 and have fun!
 
-- [aarch64-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.3.1/alejandra-aarch64-unknown-linux-musl)
-- [armv6l-unknown-linux-musleabihf](https://github.com/kamadorueda/alejandra/releases/download/0.3.1/alejandra-armv6l-unknown-linux-musleabihf)
-- [armv7l-unknown-linux-musleabihf](https://github.com/kamadorueda/alejandra/releases/download/0.3.1/alejandra-armv7l-unknown-linux-musleabihf)
-- [i686-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.3.1/alejandra-i686-unknown-linux-musl)
-- [x86_64-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.3.1/alejandra-x86_64-unknown-linux-musl)
+- [aarch64-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.4.0/alejandra-aarch64-unknown-linux-musl)
+- [armv6l-unknown-linux-musleabihf](https://github.com/kamadorueda/alejandra/releases/download/0.4.0/alejandra-armv6l-unknown-linux-musleabihf)
+- [armv7l-unknown-linux-musleabihf](https://github.com/kamadorueda/alejandra/releases/download/0.4.0/alejandra-armv7l-unknown-linux-musleabihf)
+- [i686-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.4.0/alejandra-i686-unknown-linux-musl)
+- [x86_64-unknown-linux-musl](https://github.com/kamadorueda/alejandra/releases/download/0.4.0/alejandra-x86_64-unknown-linux-musl)
 
 Alternatively there is an automated method for some platforms.
 It needs:
@@ -144,7 +144,7 @@ $ /path/to/alejandra --help
 - Nix with [Flakes](https://nixos.wiki/wiki/Flakes):
 
   ```bash
-  $ nix profile install github:kamadorueda/alejandra/0.3.1
+  $ nix profile install github:kamadorueda/alejandra/0.4.0
   ```
 
 - Nix stable:
@@ -152,10 +152,10 @@ $ /path/to/alejandra --help
   Pick one depending on your platform:
 
   ```bash
-  $ nix-env -ivA aarch64-darwin -f https://github.com/kamadorueda/alejandra/tarball/0.3.1
-  $ nix-env -ivA aarch64-linux -f https://github.com/kamadorueda/alejandra/tarball/0.3.1
-  $ nix-env -ivA x86_64-darwin -f https://github.com/kamadorueda/alejandra/tarball/0.3.1
-  $ nix-env -ivA x86_64-linux -f https://github.com/kamadorueda/alejandra/tarball/0.3.1
+  $ nix-env -ivA aarch64-darwin -f https://github.com/kamadorueda/alejandra/tarball/0.4.0
+  $ nix-env -ivA aarch64-linux -f https://github.com/kamadorueda/alejandra/tarball/0.4.0
+  $ nix-env -ivA x86_64-darwin -f https://github.com/kamadorueda/alejandra/tarball/0.4.0
+  $ nix-env -ivA x86_64-linux -f https://github.com/kamadorueda/alejandra/tarball/0.4.0
   ```
 
 Then run Alejandra with:
diff --git a/flake.lock b/flake.lock
index fef34b4..05873ae 100644
--- a/flake.lock
+++ b/flake.lock
@@ -18,11 +18,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1645013224,
-        "narHash": "sha256-b7OEC8vwzJv3rsz9pwnTX2LQDkeOWz2DbKypkVvNHXc=",
+        "lastModified": 1645347465,
+        "narHash": "sha256-GoNcKieZf86tFzuVY7+kfEGw0rjgBrdfwRj4l7zOfZw=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b66b39216b1fef2d8c33cc7a5c72d8da80b79970",
+        "rev": "7feed2c0bec4161c83509d18089784cfcef49667",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index 63e39ad..377f8ad 100644
--- a/flake.nix
+++ b/flake.nix
@@ -11,7 +11,7 @@
   outputs = inputs: let
     commit = inputs.self.shortRev or "dirty";
     date = inputs.self.lastModifiedDate or inputs.self.lastModified or "19700101";
-    version = "0.3.1+${builtins.substring 0 8 date}.${commit}";
+    version = "0.4.0+${builtins.substring 0 8 date}.${commit}";
 
     nixpkgsForHost = host:
       import inputs.nixpkgs {
diff --git a/front/Cargo.lock b/front/Cargo.lock
index 20dc0a7..301f0ff 100644
--- a/front/Cargo.lock
+++ b/front/Cargo.lock
@@ -4,7 +4,7 @@ version = 3
 
 [[package]]
 name = "alejandra_engine"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "clap",
  "rand",
@@ -14,7 +14,7 @@ dependencies = [
 
 [[package]]
 name = "alejandra_front"
-version = "0.3.1"
+version = "0.4.0"
 dependencies = [
  "alejandra_engine",
  "console_error_panic_hook",
diff --git a/front/Cargo.toml b/front/Cargo.toml
index db31328..772257e 100644
--- a/front/Cargo.toml
+++ b/front/Cargo.toml
@@ -14,7 +14,7 @@ description = "The Uncompromising Nix Code Formatter"
 edition = "2021"
 name = "alejandra_front"
 repository = "https://github.com/kamadorueda/alejandra"
-version = "0.3.1"
+version = "0.4.0"
 
 [profile.release]
 lto = true
diff --git a/front/flake.lock b/front/flake.lock
index 418378e..df4a554 100644
--- a/front/flake.lock
+++ b/front/flake.lock
@@ -8,11 +8,11 @@
         "rust-analyzer-src": "rust-analyzer-src"
       },
       "locked": {
-        "lastModified": 1645338193,
-        "narHash": "sha256-BTajZF5xFmO3+MZE29C6JRLSM6PXdoFrpTlaMZr0Ljc=",
+        "lastModified": 1645424702,
+        "narHash": "sha256-qxT0Mu7/xnMWDygGhctmvQvG1+xz+mmV692GRBkjDFk=",
         "owner": "nix-community",
         "repo": "fenix",
-        "rev": "f15f0f9fedd87e265e49585463df72c1257f1ae8",
+        "rev": "882a812300adcd85a5e10dc26e5d7a1d6acc7575",
         "type": "github"
       },
       "original": {
@@ -23,11 +23,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1645013224,
-        "narHash": "sha256-b7OEC8vwzJv3rsz9pwnTX2LQDkeOWz2DbKypkVvNHXc=",
+        "lastModified": 1645347465,
+        "narHash": "sha256-GoNcKieZf86tFzuVY7+kfEGw0rjgBrdfwRj4l7zOfZw=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "b66b39216b1fef2d8c33cc7a5c72d8da80b79970",
+        "rev": "7feed2c0bec4161c83509d18089784cfcef49667",
         "type": "github"
       },
       "original": {
@@ -46,11 +46,11 @@
     "rust-analyzer-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1645265362,
-        "narHash": "sha256-6z88g8cyw6Ae9SxgGUmT+jMuMadrJ4IgVV+UHdK4ook=",
+        "lastModified": 1645399019,
+        "narHash": "sha256-O9onJrAJY0TWxEZZcTWuF7SGPypRtSo0ZbpzDLC5+os=",
         "owner": "rust-analyzer",
         "repo": "rust-analyzer",
-        "rev": "1d53f695f0408f47c5cce5cefa471eb0e86b0db7",
+        "rev": "d6ed146a1caa41c65a831efbc80d79067c8f5955",
         "type": "github"
       },
       "original": {
diff --git a/installers/aarch64-linux.sh b/installers/aarch64-linux.sh
index 9f38ff8..a2850ce 100755
--- a/installers/aarch64-linux.sh
+++ b/installers/aarch64-linux.sh
@@ -2,7 +2,7 @@
 
 releases=https://github.com/kamadorueda/alejandra/releases/download/
 target=alejandra-aarch64-unknown-linux-musl
-version=0.3.1
+version=0.4.0
 
 curl -o alejandra -L "${releases}/${version}/${target}"
 
diff --git a/installers/x86_64-linux.sh b/installers/x86_64-linux.sh
index 1d26f09..e783668 100755
--- a/installers/x86_64-linux.sh
+++ b/installers/x86_64-linux.sh
@@ -2,7 +2,7 @@
 
 releases=https://github.com/kamadorueda/alejandra/releases/download/
 target=alejandra-x86_64-unknown-linux-musl
-version=0.3.1
+version=0.4.0
 
 curl -o alejandra -L "${releases}/${version}/${target}"
 
diff --git a/pre-commit.sh b/pre-commit.sh
deleted file mode 100644
index 3e365e2..0000000
--- a/pre-commit.sh
+++ /dev/null
@@ -1,23 +0,0 @@
-#!/usr/bin/env bash
-
-if git rev-parse --verify HEAD > /dev/null 2>&1; then
-  against=HEAD
-else
-  # Initial commit: diff against an empty tree object
-  against=$(${git}/bin/git hash-object -t tree /dev/null)
-fi
-
-diff="git diff-index --name-only --cached $against --diff-filter d"
-all_files=($($diff))
-
-# Format the entire tree.
-treefmt
-
-# check editorconfig
-editorconfig-checker -- "${all_files[@]}"
-if [[ $? != '0' ]]; then
-  printf "%b\n" \
-    "\nCode is not aligned with .editorconfig" \
-    "Review the output and commit your fixes" >&2
-  exit 1
-fi
diff --git a/src/alejandra_cli/Cargo.toml b/src/alejandra_cli/Cargo.toml
index 9914132..09b5f3b 100644
--- a/src/alejandra_cli/Cargo.toml
+++ b/src/alejandra_cli/Cargo.toml
@@ -18,4 +18,4 @@ description = "The Uncompromising Nix Code Formatter"
 edition = "2021"
 name = "alejandra_cli"
 repository = "https://github.com/kamadorueda/alejandra"
-version = "0.3.1"
+version = "0.4.0"
diff --git a/src/alejandra_engine/Cargo.toml b/src/alejandra_engine/Cargo.toml
index 641dc63..e3aeb90 100644
--- a/src/alejandra_engine/Cargo.toml
+++ b/src/alejandra_engine/Cargo.toml
@@ -10,4 +10,4 @@ description = "The Uncompromising Nix Code Formatter"
 edition = "2021"
 name = "alejandra_engine"
 repository = "https://github.com/kamadorueda/alejandra"
-version = "0.3.1"
+version = "0.4.0"
diff --git a/src/alejandra_engine/src/version.rs b/src/alejandra_engine/src/version.rs
index 737f478..f22e72f 100644
--- a/src/alejandra_engine/src/version.rs
+++ b/src/alejandra_engine/src/version.rs
@@ -1 +1 @@
-pub const VERSION: &str = "0.3.1";
+pub const VERSION: &str = "0.4.0";