Remove hardcoded master reference in end commit bound

Author: Kobzol

src/bounds.rs

@@ -93,7 +93,7 @@ impl Bounds {
             }
             (Some(Bound::Commit(start)), None) => Bounds::Commits {
                 start,
-                end: args.access.repo().commit("origin/master")?.sha,
+                end: args.access.repo().commit("HEAD")?.sha,
             },
             (None, Some(Bound::Commit(end))) => Bounds::Commits {
                 start: EPOCH_COMMIT.to_string(),

src/github.rs

@@ -224,16 +224,8 @@ impl ToUrl for CommitsUrl<'_> {
 
 impl ToUrl for CommitDetailsUrl<'_> {
     fn url(&self) -> String {
-        // "origin/master" is set as `sha` when there is no `--end=` definition
-        // specified on the command line.  We define the GitHub master branch
-        // HEAD commit as the end commit in this case
-        let reference = if self.sha == "origin/master" {
-            "master"
-        } else {
-            self.sha
-        };
-
-        format!("https://api.github.com/repos/{OWNER}/{REPO}/compare/master...{reference}")
+        let reference = self.sha;
+        format!("https://api.github.com/repos/{OWNER}/{REPO}/compare/HEAD...{reference}")
     }
 }
 

src/main.rs

@@ -1000,7 +1000,7 @@ impl Config {
             if c.committer.name != BORS_AUTHOR {
                 bail!(
                     "Expected author {} to be {BORS_AUTHOR} for {}.\n \
-                     Make sure specified commits are on the master branch \
+                     Make sure specified commits are on the default branch \
                      and refer to a bors merge commit!",
                     c.committer.name,
                     c.sha

src/repo_access.rs

@@ -12,7 +12,7 @@ pub(crate) trait RustRepositoryAccessor {
     }
 
     /// Looks up commit associated with `commit_ref`, which can be either a sha
-    /// or a more general reference like "origin/master".
+    /// or a more general reference like "origin/HEAD".
     /// If `commit_ref` is a commit forked from the "mainline" git history
     /// (e.g. a stable tag like `1.88.0`), returns the merge base of the given commit reference.
     fn commit(&self, commit_ref: &str) -> anyhow::Result<Commit>;
@@ -33,7 +33,7 @@ impl RustRepositoryAccessor for AccessViaLocalGit {
         git::get_commit(commit_ref)
     }
     fn commits(&self, start_sha: &str, end_sha: &str) -> anyhow::Result<Vec<Commit>> {
-        let end_sha = if end_sha == "origin/master" {
+        let end_sha = if end_sha == "HEAD" {
             "FETCH_HEAD"
         } else {
             end_sha