Add SOURCE_DATE_EPOCH to build

Add an optional SOURCE_DATE_EPOCH environment variable, to make the builds reproducible.

Co-authored-by: Tim Oram <[email protected]>
Co-authored-by: Bernhard M. Wiedemann <[email protected]>

Author: bmwiedemann

README.md

@@ -256,12 +256,16 @@ An addition to the report printed to the CLI, an HTML report can be found in the
 
 ### Release
 
-##### Building
+#### Debian Building
 
     cargo make deb
 
 A deb file will be written to `target/debian/interactive-rebase-tool_*.deb`.
 
+#### Reproducible Builds
+
+Providing a [`SOURCE_DATE_EPOCH`](https://reproducible-builds.org/specs/source-date-epoch/#idm55) environment variable with a valid UNIX timestamp, defined in seconds, will ensure a reproducible build.
+
 ## Related Projects
 
 * [rebase-editor](https://github.com/sjurba/rebase-editor) is a very similar project written in Node.js.

src/core/build.rs

@@ -1,6 +1,6 @@
-use std::process;
+use std::{env, process};
 
-use chrono::Utc;
+use chrono::{TimeZone, Utc};
 use rustc_version::{version_meta, Channel};
 
 fn main() {
@@ -16,7 +16,13 @@ fn main() {
 	if let Some(rev) = git_revision_hash() {
 		println!("cargo:rustc-env=GIRT_BUILD_GIT_HASH={rev}");
 	}
-	println!("cargo:rustc-env=GIRT_BUILD_DATE={}", Utc::now().format("%Y-%m-%d"));
+
+	// Use provided SOURCE_DATE_EPOCH to make builds reproducible
+	let build_date = match env::var("SOURCE_DATE_EPOCH") {
+		Ok(val) => Utc.timestamp_opt(val.parse::<i64>().unwrap(), 0).unwrap(),
+		Err(_) => Utc::now(),
+	};
+	println!("cargo:rustc-env=GIRT_BUILD_DATE={}", build_date.format("%Y-%m-%d"));
 }
 
 fn git_revision_hash() -> Option<String> {