git: remove ": {source}" from FailedRefExportReason, walk chain by caller

The error output gets more verbose because all gix error sources are printed.
Maybe we'll need a better formatting, but changing to multi-line output doesn't
look nice either.

cli/src/git_util.rs

@@ -19,6 +19,7 @@ use std::path::{Path, PathBuf};
 use std::process::Stdio;
 use std::sync::Mutex;
 use std::time::Instant;
+use std::{error, iter};
 
 use jj_lib::git::{self, FailedRefExport, FailedRefExportReason, GitImportStats};
 use jj_lib::git_backend::GitBackend;
@@ -172,7 +173,10 @@ pub fn print_failed_git_export(
         for FailedRefExport { name, reason } in failed_branches {
             formatter.write_str("  ")?;
             write!(formatter.labeled("branch"), "{name}")?;
-            writeln!(formatter, ": {reason}")?;
+            for err in iter::successors(Some(reason as &dyn error::Error), |err| err.source()) {
+                write!(formatter, ": {err}")?;
+            }
+            writeln!(formatter)?;
         }
         drop(formatter);
         if failed_branches

cli/tests/test_git_colocated.rs

@@ -402,13 +402,15 @@ fn test_git_colocated_conflicting_git_refs() {
     test_env.jj_cmd_ok(&workspace_root, &["branch", "create", "main"]);
     let (stdout, stderr) = test_env.jj_cmd_ok(&workspace_root, &["branch", "create", "main/sub"]);
     insta::assert_snapshot!(stdout, @"");
-    insta::assert_snapshot!(stderr, @r###"
-    Failed to export some branches:
-      main/sub: Failed to set: A lock could not be obtained for reference "refs/heads/main/sub"
-    Hint: Git doesn't allow a branch name that looks like a parent directory of
-    another (e.g. `foo` and `foo/bar`). Try to rename the branches that failed to
-    export or their "parent" branches.
-    "###);
+    insta::with_settings!({filters => vec![(": The lock for resource.*", ": ...")]}, {
+        insta::assert_snapshot!(stderr, @r###"
+        Failed to export some branches:
+          main/sub: Failed to set: A lock could not be obtained for reference "refs/heads/main/sub": ...
+        Hint: Git doesn't allow a branch name that looks like a parent directory of
+        another (e.g. `foo` and `foo/bar`). Try to rename the branches that failed to
+        export or their "parent" branches.
+        "###);
+    });
 }
 
 #[test]

cli/tests/test_git_import_export.rs

@@ -67,13 +67,15 @@ fn test_git_export_conflicting_git_refs() {
     test_env.jj_cmd_ok(&repo_path, &["branch", "create", "main/sub"]);
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["git", "export"]);
     insta::assert_snapshot!(stdout, @"");
-    insta::assert_snapshot!(stderr, @r###"
-    Failed to export some branches:
-      main/sub: Failed to set: A lock could not be obtained for reference "refs/heads/main/sub"
-    Hint: Git doesn't allow a branch name that looks like a parent directory of
-    another (e.g. `foo` and `foo/bar`). Try to rename the branches that failed to
-    export or their "parent" branches.
-    "###);
+    insta::with_settings!({filters => vec![(": The lock for resource.*", ": ...")]}, {
+        insta::assert_snapshot!(stderr, @r###"
+        Failed to export some branches:
+          main/sub: Failed to set: A lock could not be obtained for reference "refs/heads/main/sub": ...
+        Hint: Git doesn't allow a branch name that looks like a parent directory of
+        another (e.g. `foo` and `foo/bar`). Try to rename the branches that failed to
+        export or their "parent" branches.
+        "###);
+    });
 }
 
 #[test]

lib/src/git.rs

@@ -592,10 +592,10 @@ pub enum FailedRefExportReason {
     #[error("Modified ref had been deleted in Git")]
     ModifiedInJjDeletedInGit,
     /// Failed to delete the ref from the Git repo
-    #[error("Failed to delete: {0}")]
+    #[error("Failed to delete")]
     FailedToDelete(#[source] Box<gix::reference::edit::Error>),
     /// Failed to set the ref in the Git repo
-    #[error("Failed to set: {0}")]
+    #[error("Failed to set")]
     FailedToSet(#[source] Box<gix::reference::edit::Error>),
 }