Allow the release info build script to work without requiring Git to be installed (#3105)

* Prevent panic if env GRAPHITE_GIT_COMMIT_HASH is less than 8 chars long

* Improve release info build script

* Nits

---------

Co-authored-by: Keavon Chambers <[email protected]>

Author: timon-schelling

editor/build.rs

@@ -1,24 +1,60 @@
+use std::env;
 use std::process::Command;
 
 const GRAPHITE_RELEASE_SERIES: &str = "Alpha 4";
 
 fn main() {
-	// Execute a Git command for its stdout. Early exit if it fails for any of the possible reasons.
-	let try_git_command = |args: &[&str]| -> Option<String> {
-		let git_output = Command::new("git").args(args).output().ok()?;
-		let maybe_empty = String::from_utf8(git_output.stdout).ok()?;
-		let command_result = (!maybe_empty.is_empty()).then_some(maybe_empty)?;
-		Some(command_result)
-	};
-	// Execute a Git command for its output. Return "unknown" if it fails for any of the possible reasons.
-	let git_command = |args| -> String { try_git_command(args).unwrap_or_else(|| String::from("unknown")) };
-
-	// Rather than printing to any terminal, these commands set environment variables in the Cargo toolchain.
-	// They are accessed with the `env!("...")` macro in the codebase.
-	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_DATE={}", git_command(&["log", "-1", "--format=%cd"]));
-	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_HASH={}", git_command(&["rev-parse", "HEAD"]));
-	let branch = std::env::var("GITHUB_HEAD_REF").unwrap_or_default();
-	let branch = if branch.is_empty() { git_command(&["name-rev", "--name-only", "HEAD"]) } else { branch };
-	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_BRANCH={branch}");
+	// Instruct Cargo to rerun this build script if any of these environment variables change.
+	println!("cargo:rerun-if-env-changed=GRAPHITE_GIT_COMMIT_DATE");
+	println!("cargo:rerun-if-env-changed=GRAPHITE_GIT_COMMIT_HASH");
+	println!("cargo:rerun-if-env-changed=GRAPHITE_GIT_COMMIT_BRANCH");
+	println!("cargo:rerun-if-env-changed=GITHUB_HEAD_REF");
+
+	// Instruct Cargo to rerun this build script if the Git HEAD or refs change.
+	println!("cargo:rerun-if-changed=.git/HEAD");
+	println!("cargo:rerun-if-changed=.git/refs/heads");
+
+	// Try to get the commit information from the environment (e.g. set by CI), otherwise fall back to Git commands.
+	let commit_date = env_or_else("GRAPHITE_GIT_COMMIT_DATE", || git_or_unknown(&["log", "-1", "--format=%cI"]));
+	let commit_hash = env_or_else("GRAPHITE_GIT_COMMIT_HASH", || git_or_unknown(&["rev-parse", "HEAD"]));
+	let commit_branch = env_or_else("GRAPHITE_GIT_COMMIT_BRANCH", || {
+		let gh = env::var("GITHUB_HEAD_REF").unwrap_or_default();
+		if !gh.trim().is_empty() {
+			gh.trim().to_string()
+		} else {
+			git_or_unknown(&["rev-parse", "--abbrev-ref", "HEAD"])
+		}
+	});
+
+	// Instruct Cargo to set environment variables for compile time.
+	// They are accessed with the `env!("GRAPHITE_*")` macro in the codebase.
+	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_DATE={commit_date}");
+	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_HASH={commit_hash}");
+	println!("cargo:rustc-env=GRAPHITE_GIT_COMMIT_BRANCH={commit_branch}");
 	println!("cargo:rustc-env=GRAPHITE_RELEASE_SERIES={GRAPHITE_RELEASE_SERIES}");
 }
+
+/// Get an environment variable, or if it is not set or empty, use the provided fallback function. Returns a string with trimmed whitespace.
+fn env_or_else(key: &str, fallback: impl FnOnce() -> String) -> String {
+	match env::var(key) {
+		Ok(v) if !v.trim().is_empty() => v.trim().to_string(),
+		_ => fallback().trim().to_string(),
+	}
+}
+
+/// Execute a Git command to obtain its output. Return "unknown" if it fails for any of the possible reasons.
+fn git_or_unknown(args: &[&str]) -> String {
+	git(args).unwrap_or_else(|| "unknown".to_string())
+}
+
+/// Run a git command and capture trimmed stdout.
+/// Returns None if git is missing, exits with error, or stdout is empty/non-UTF8.
+fn git(args: &[&str]) -> Option<String> {
+	let output = Command::new("git").args(args).output().ok()?;
+	if !output.status.success() {
+		return None;
+	}
+	let s = String::from_utf8(output.stdout).ok()?;
+	let t = s.trim();
+	if t.is_empty() { None } else { Some(t.to_string()) }
+}

editor/src/application.rs

@@ -51,7 +51,7 @@ pub fn commit_info_localized(localized_commit_date: &str) -> String {
 		{}",
 		GRAPHITE_RELEASE_SERIES,
 		GRAPHITE_GIT_COMMIT_BRANCH,
-		&GRAPHITE_GIT_COMMIT_HASH[..8],
+		GRAPHITE_GIT_COMMIT_HASH.get(..8).unwrap_or(GRAPHITE_GIT_COMMIT_HASH),
 		localized_commit_date
 	)
 }