leverage error propagation to avoid error-prone repetitive error mapping

src/constants.rs

@@ -1,6 +1,17 @@
 pub const AUTO_MERGE_REQUEST: &str = "bot merge";
 pub const AUTO_MERGE_FORCE: &str = "bot merge force";
 pub const AUTO_MERGE_CANCEL: &str = "bot merge cancel";
+pub const REBASE: &str = "bot rebase";
+pub const BURNIN_REQUEST: &str = "bot burnin";
+pub const COMPARE_RELEASE_REQUEST: &str = "bot compare substrate";
+pub const BOT_COMMANDS: [&str; 6] = [
+	AUTO_MERGE_REQUEST,
+	AUTO_MERGE_FORCE,
+	AUTO_MERGE_CANCEL,
+	REBASE,
+	BURNIN_REQUEST,
+	COMPARE_RELEASE_REQUEST,
+];
 
 pub const AUTO_MERGE_FAILED: &str = "Cannot merge; please ensure the pull request is mergeable and has approval from the project owner or at least {min_reviewers} core devs.";
 pub const AUTO_MERGE_CHECKS_FAILED: &str = "Checks failed; cannot auto-merge.";
@@ -9,10 +20,6 @@ pub const AUTO_MERGE_CHECKS_ERROR: &str =
 pub const AUTO_MERGE_INVALIDATED: &str =
 	"Something has changed since auto-merge was requested; cancelling.";
 
-pub const COMPARE_RELEASE_REQUEST: &str = "bot compare substrate";
-pub const REBASE: &str = "bot rebase";
-pub const BURNIN_REQUEST: &str = "bot burnin";
-
 pub const FEATURES_KEY: &str = "features";
 
 pub const PROJECT_NEEDS_BACKLOG: &str =

src/error.rs

@@ -16,25 +16,31 @@ pub enum Error {
 		field: String,
 	},
 
-	#[snafu(display("Error updating companion: {}", source))]
-	Companion {
-		source: Box<Error>,
-	},
-
 	#[snafu(display("Error merging: {}", source))]
 	Merge {
 		source: Box<Error>,
 		commit_sha: String,
 	},
 
+	#[snafu(display("Companion update failed: {}", source))]
+	CompanionUpdate {
+		source: Box<Error>,
+	},
+
+	#[snafu(display("Rebase failed: {}", source))]
+	Rebase {
+		source: Box<Error>,
+	},
+
 	#[snafu(display("Checks failed for {}", commit_sha))]
 	ChecksFailed {
 		commit_sha: String,
 	},
 
-	#[snafu(display("Head SHA changed from {}", commit_sha))]
+	#[snafu(display("Head SHA changed from {} to {}", expected, actual))]
 	HeadChanged {
-		commit_sha: String,
+		expected: String,
+		actual: String,
 	},
 
 	#[snafu(display("Error getting organization membership: {}", source))]
@@ -53,7 +59,7 @@ pub enum Error {
 	#[snafu(display("Missing approval."))]
 	Approval {},
 
-	#[snafu(display("Error: {}", msg))]
+	#[snafu(display("{}", msg))]
 	Message {
 		msg: String,
 	},
@@ -171,7 +177,7 @@ pub enum Error {
 	},
 
 	#[snafu(display(
-		"Cmd '{}' failed with status {:?}; output: {}",
+		"Command '{}' failed with status {:?}; output: {}",
 		cmd,
 		status_code,
 		err

src/github.rs

@@ -1,4 +1,4 @@
-use crate::{error::*, Result, PR_HTML_URL_REGEX};
+use crate::{constants::BOT_COMMANDS, error::*, Result, PR_HTML_URL_REGEX};
 use regex::Regex;
 use serde::{Deserialize, Serialize};
 use snafu::OptionExt;
@@ -784,7 +784,9 @@ impl DetectUserCommentPullRequest {
 				}),
 		} = self
 		{
-			if body.trim().starts_with("bot ") {
+			let body = body.trim();
+
+			if BOT_COMMANDS.iter().find(|cmd| **cmd == body).is_some() {
 				if let Some(DetectUserCommentPullRequestRepository {
 					name: Some(name),
 					owner: Some(User { login, .. }),