refactor: split Rust backend into sub-modules — git, theme, github, frontmatter, commands

- git.rs (1907 lines) → 7 files: mod, history, status, commit, remote, conflict, pulse
- theme.rs (1075 lines) → 4 files: mod, defaults, seed, create
- github.rs (886 lines) → 4 files: mod, api, auth, clone
- frontmatter.rs (827 lines) → 3 files: mod, yaml, ops
- lib.rs (772 lines) → lib.rs (160) + commands.rs (650)

484 tests pass, clippy clean, rustfmt clean, coverage 85.42%

src-tauri/src/git/remote.rs

@@ -0,0 +1,246 @@
+use serde::{Deserialize, Serialize};
+use std::path::Path;
+use std::process::Command;
+
+use super::conflict::get_conflict_files;
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
+pub struct GitPullResult {
+    pub status: String, // "up_to_date" | "updated" | "conflict" | "no_remote" | "error"
+    pub message: String,
+    #[serde(rename = "updatedFiles")]
+    pub updated_files: Vec<String>,
+    #[serde(rename = "conflictFiles")]
+    pub conflict_files: Vec<String>,
+}
+
+/// Check whether the vault repo has at least one remote configured.
+pub fn has_remote(vault_path: &str) -> Result<bool, String> {
+    let vault = Path::new(vault_path);
+    let output = Command::new("git")
+        .args(["remote"])
+        .current_dir(vault)
+        .output()
+        .map_err(|e| format!("Failed to run git remote: {}", e))?;
+
+    Ok(!String::from_utf8_lossy(&output.stdout).trim().is_empty())
+}
+
+/// Pull latest changes from remote. Uses --no-rebase to merge.
+/// Returns a structured result with status and affected files.
+pub fn git_pull(vault_path: &str) -> Result<GitPullResult, String> {
+    let vault = Path::new(vault_path);
+
+    if !has_remote(vault_path)? {
+        return Ok(GitPullResult {
+            status: "no_remote".to_string(),
+            message: "No remote configured".to_string(),
+            updated_files: vec![],
+            conflict_files: vec![],
+        });
+    }
+
+    let output = Command::new("git")
+        .args(["pull", "--no-rebase"])
+        .current_dir(vault)
+        .output()
+        .map_err(|e| format!("Failed to run git pull: {}", e))?;
+
+    let stdout = String::from_utf8_lossy(&output.stdout).to_string();
+    let stderr = String::from_utf8_lossy(&output.stderr).to_string();
+
+    if output.status.success() {
+        if stdout.contains("Already up to date") || stdout.contains("Already up-to-date") {
+            return Ok(GitPullResult {
+                status: "up_to_date".to_string(),
+                message: "Already up to date".to_string(),
+                updated_files: vec![],
+                conflict_files: vec![],
+            });
+        }
+        let updated = parse_updated_files(&stdout);
+        return Ok(GitPullResult {
+            status: "updated".to_string(),
+            message: format!("{} file(s) updated", updated.len()),
+            updated_files: updated,
+            conflict_files: vec![],
+        });
+    }
+
+    // Check for merge conflicts
+    let conflicts = get_conflict_files(vault_path).unwrap_or_default();
+    if !conflicts.is_empty() {
+        return Ok(GitPullResult {
+            status: "conflict".to_string(),
+            message: format!("Merge conflict in {} file(s)", conflicts.len()),
+            updated_files: vec![],
+            conflict_files: conflicts,
+        });
+    }
+
+    // Network error or other failure — report as error
+    let detail = if stderr.trim().is_empty() {
+        stdout.trim().to_string()
+    } else {
+        stderr.trim().to_string()
+    };
+    Ok(GitPullResult {
+        status: "error".to_string(),
+        message: detail,
+        updated_files: vec![],
+        conflict_files: vec![],
+    })
+}
+
+/// Parse `git pull` output to extract updated file paths.
+fn parse_updated_files(stdout: &str) -> Vec<String> {
+    stdout
+        .lines()
+        .filter_map(|line| {
+            let trimmed = line.trim();
+            // Lines like " path/to/file.md | 5 ++-" in diffstat
+            if trimmed.contains('|') {
+                let path = trimmed.split('|').next()?.trim();
+                if !path.is_empty() {
+                    return Some(path.to_string());
+                }
+            }
+            None
+        })
+        .collect()
+}
+
+/// Push to remote.
+pub fn git_push(vault_path: &str) -> Result<String, String> {
+    let vault = Path::new(vault_path);
+
+    let output = Command::new("git")
+        .args(["push"])
+        .current_dir(vault)
+        .output()
+        .map_err(|e| format!("Failed to run git push: {}", e))?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        return Err(format!("git push failed: {}", stderr));
+    }
+
+    // git push often writes to stderr even on success
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    Ok(format!("{}{}", stdout, stderr))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::git::git_commit;
+    use crate::git::tests::{setup_git_repo, setup_remote_pair};
+    use std::fs;
+    use std::process::Command;
+
+    #[test]
+    fn test_has_remote_returns_false_for_local_repo() {
+        let dir = setup_git_repo();
+        let vault = dir.path();
+        let vp = vault.to_str().unwrap();
+
+        assert!(!has_remote(vp).unwrap());
+    }
+
+    #[test]
+    fn test_has_remote_returns_true_when_remote_exists() {
+        let dir = setup_git_repo();
+        let vault = dir.path();
+        let vp = vault.to_str().unwrap();
+
+        Command::new("git")
+            .args(["remote", "add", "origin", "https://example.com/repo.git"])
+            .current_dir(vault)
+            .output()
+            .unwrap();
+
+        assert!(has_remote(vp).unwrap());
+    }
+
+    #[test]
+    fn test_git_pull_no_remote_returns_no_remote() {
+        let dir = setup_git_repo();
+        let vault = dir.path();
+        let vp = vault.to_str().unwrap();
+
+        fs::write(vault.join("note.md"), "# Note\n").unwrap();
+        git_commit(vp, "initial").unwrap();
+
+        let result = git_pull(vp).unwrap();
+        assert_eq!(result.status, "no_remote");
+        assert!(result.updated_files.is_empty());
+        assert!(result.conflict_files.is_empty());
+    }
+
+    #[test]
+    fn test_git_pull_up_to_date() {
+        let (_bare, clone_a, _clone_b) = setup_remote_pair();
+        let vp_a = clone_a.path().to_str().unwrap();
+
+        fs::write(clone_a.path().join("note.md"), "# Note\n").unwrap();
+        git_commit(vp_a, "initial").unwrap();
+        git_push(vp_a).unwrap();
+
+        let result = git_pull(vp_a).unwrap();
+        assert_eq!(result.status, "up_to_date");
+    }
+
+    #[test]
+    fn test_git_pull_updated_files() {
+        let (_bare, clone_a, clone_b) = setup_remote_pair();
+        let vp_a = clone_a.path().to_str().unwrap();
+        let vp_b = clone_b.path().to_str().unwrap();
+
+        fs::write(clone_a.path().join("note.md"), "# Note\n").unwrap();
+        git_commit(vp_a, "initial").unwrap();
+        git_push(vp_a).unwrap();
+
+        git_pull(vp_b).unwrap();
+
+        fs::write(clone_a.path().join("note.md"), "# Updated Note\n").unwrap();
+        git_commit(vp_a, "update note").unwrap();
+        git_push(vp_a).unwrap();
+
+        let result = git_pull(vp_b).unwrap();
+        assert_eq!(result.status, "updated");
+        assert!(result.conflict_files.is_empty());
+    }
+
+    #[test]
+    fn test_parse_updated_files_diffstat() {
+        let stdout =
+            " Fast-forward\n note.md | 2 +-\n project/plan.md | 4 ++--\n 2 files changed\n";
+        let files = parse_updated_files(stdout);
+        assert_eq!(files, vec!["note.md", "project/plan.md"]);
+    }
+
+    #[test]
+    fn test_parse_updated_files_empty() {
+        let stdout = "Already up to date.\n";
+        let files = parse_updated_files(stdout);
+        assert!(files.is_empty());
+    }
+
+    #[test]
+    fn test_git_pull_result_serialization() {
+        let result = GitPullResult {
+            status: "updated".to_string(),
+            message: "2 file(s) updated".to_string(),
+            updated_files: vec!["note.md".to_string()],
+            conflict_files: vec![],
+        };
+        let json = serde_json::to_string(&result).unwrap();
+        assert!(json.contains("\"updatedFiles\""));
+        assert!(json.contains("\"conflictFiles\""));
+
+        let parsed: GitPullResult = serde_json::from_str(&json).unwrap();
+        assert_eq!(parsed.status, "updated");
+        assert_eq!(parsed.updated_files.len(), 1);
+    }
+}