fix(git): preserve merge commits in rtk git log

src/cmds/git/git.rs

@@ -436,6 +436,43 @@ fn run_log(
     let mut cmd = git_cmd(global_args);
     cmd.arg("log");
 
+    let (log_args, limit, user_set_limit, has_format_flag) = build_log_args(args);
+    cmd.args(log_args);
+
+    let result = exec_capture(&mut cmd).context("Failed to run git log")?;
+
+    if !result.success() {
+        eprintln!("{}", result.stderr);
+        return Ok(result.exit_code);
+    }
+
+    if verbose > 0 {
+        eprintln!("Git log output:");
+    }
+
+    // Post-process: truncate long messages, cap lines only if RTK set the default
+    let filtered = filter_log_output(&result.stdout, limit, user_set_limit, has_format_flag);
+    let filtered = never_worse(&result.stdout, &filtered).to_string();
+    println!("{}", filtered);
+
+    timer.track(
+        &format!("git log {}", args.join(" ")),
+        &format!("rtk git log {}", args.join(" ")),
+        &result.stdout,
+        &filtered,
+    );
+
+    Ok(0)
+}
+
+/// Build the arguments that RTK adds around the user's git log arguments.
+///
+/// Merge commits are deliberately left in the history. They carry topology and
+/// often identify the repository's actual integration state, so silently adding
+/// --no-merges would make the compact output semantically incorrect.
+fn build_log_args(args: &[String]) -> (Vec<String>, usize, bool, bool) {
+    let mut log_args = Vec::new();
+
     // Check if user provided format flags
     let has_format_flag = args.iter().any(|arg| {
         arg.starts_with("--oneline") || arg.starts_with("--pretty") || arg.starts_with("--format")
@@ -452,7 +489,7 @@ fn run_log(
     // Use %b (body) to preserve first line of commit body for agent context
     // (BREAKING CHANGE, Closes #xxx, design notes)
     if !has_format_flag {
-        cmd.args(["--pretty=format:%h %s (%ar) <%an>%n%b%n---END---"]);
+        log_args.push("--pretty=format:%h %s (%ar) <%an>%n%b%n---END---".to_string());
     }
 
     // Determine limit: respect user's explicit -N flag, use sensible defaults otherwise
@@ -462,52 +499,18 @@ fn run_log(
         (n, true)
     } else if has_format_flag {
         // --oneline / --pretty without -N: user wants compact output, allow more
-        cmd.arg("-50");
+        log_args.push("-50".to_string());
         (50, false)
     } else {
         // No flags at all: default to 10
-        cmd.arg("-10");
+        log_args.push("-10".to_string());
         (10, false)
     };
 
-    // Only add --no-merges if user didn't explicitly request merge commits
-    let wants_merges = args
-        .iter()
-        .any(|arg| arg == "--merges" || arg == "--min-parents=2" || arg == "--no-merges");
-    // Don't add --no-merges if user explicitly requested merges or an exact count (-n N / --max-count)
-    if !wants_merges && !has_limit_flag {
-        cmd.arg("--no-merges");
-    }
-
     // Pass all user arguments
-    for arg in args {
-        cmd.arg(arg);
-    }
-
-    let result = exec_capture(&mut cmd).context("Failed to run git log")?;
-
-    if !result.success() {
-        eprintln!("{}", result.stderr);
-        return Ok(result.exit_code);
-    }
-
-    if verbose > 0 {
-        eprintln!("Git log output:");
-    }
-
-    // Post-process: truncate long messages, cap lines only if RTK set the default
-    let filtered = filter_log_output(&result.stdout, limit, user_set_limit, has_format_flag);
-    let filtered = never_worse(&result.stdout, &filtered).to_string();
-    println!("{}", filtered);
+    log_args.extend(args.iter().cloned());
 
-    timer.track(
-        &format!("git log {}", args.join(" ")),
-        &format!("rtk git log {}", args.join(" ")),
-        &result.stdout,
-        &filtered,
-    );
-
-    Ok(0)
+    (log_args, limit, user_set_limit, has_format_flag)
 }
 
 /// Filter git log output: truncate long messages, cap lines
@@ -2731,6 +2734,23 @@ A  added.rs
         assert_eq!(parse_user_limit(&args), None);
     }
 
+    #[test]
+    fn test_build_log_args_preserves_merge_commits() {
+        let (args, limit, user_set_limit, user_format) = build_log_args(&[]);
+
+        assert_eq!(limit, 10);
+        assert!(!user_set_limit);
+        assert!(!user_format);
+        assert!(
+            !args.iter().any(|arg| arg == "--no-merges"),
+            "default git log must not hide merge commits"
+        );
+        assert!(
+            args.iter().any(|arg| arg.starts_with("--pretty=format:")),
+            "default git log should still use RTK's compact format"
+        );
+    }
+
     #[test]
     fn test_filter_log_output_token_savings() {
         fn count_tokens(text: &str) -> usize {