diff --git a/CHANGELOG.md b/CHANGELOG.md
index 575d09b..4a1a66f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,9 +2,6 @@
 
 ## [Unreleased]
 
-### Added
-- `sync` subcommand, which performs git pull (fast-forward) and push (#21)
-
 ### Fixed
 - Git local config is now looked up. (#20)
 - Git global config will not be polluted in test by default. (#20)
diff --git a/src/cmd_sync.rs b/src/cmd_sync.rs
index 9611c7a..2c2a213 100644
--- a/src/cmd_sync.rs
+++ b/src/cmd_sync.rs
@@ -1,10 +1,7 @@
-use std::{
-    io::{self, Write},
-    path::{Path, PathBuf},
-};
+use std::path::{Path, PathBuf};
 
-use anyhow::{anyhow, Context, Result};
-use git2::{build::CheckoutBuilder, Cred, FetchOptions, PushOptions, RemoteCallbacks, Repository};
+use anyhow::{anyhow, Result};
+use git2::{Cred, PushOptions, RemoteCallbacks, Repository};
 
 pub(crate) fn cmd_sync(
     config_dir: &PathBuf,
@@ -12,7 +9,7 @@ pub(crate) fn cmd_sync(
     use_sshagent: bool,
     ssh_key: Option<PathBuf>,
 ) -> Result<()> {
-    info!("cmd_sync");
+    warn!("Experimental");
     let repo = Repository::open(config_dir)?;
     let remote_name = match remote_name {
         Some(remote_name) => remote_name,
@@ -24,34 +21,12 @@ pub(crate) fn cmd_sync(
             remotes.get(0).unwrap().to_string()
         }
     };
-    debug!("resolved remote name: {remote_name}");
 
-    let mut remote = repo.find_remote(&remote_name)?;
-
-    pull(
-        &repo,
-        &mut remote,
-        remote_name,
-        &use_sshagent,
-        ssh_key.as_ref(),
-    )?;
-
-    push(&repo, &mut remote, &use_sshagent, ssh_key.as_ref())?;
-    Ok(())
-}
-
-fn remote_callback<'b, 'a>(
-    use_sshagent: &'a bool,
-    ssh_key: Option<&'a PathBuf>,
-) -> RemoteCallbacks<'a>
-where
-    'b: 'a,
-{
     // using credentials
     let mut callbacks = RemoteCallbacks::new();
     callbacks
-        .credentials(move |_url, username_from_url, _allowed_types| {
-            if let Some(key) = ssh_key {
+        .credentials(|_url, username_from_url, _allowed_types| {
+            if let Some(key) = &ssh_key {
                 info!("Using provided ssh key to access the repository");
                 let passwd = match inquire::Password::new("SSH passphrase").prompt() {
                     std::result::Result::Ok(s) => Some(s),
@@ -67,7 +42,7 @@ where
                     key as &Path,
                     passwd.as_deref(),
                 )
-            } else if *use_sshagent {
+            } else if use_sshagent {
                 // use ssh agent
                 info!("Using ssh agent to access the repository");
                 Cred::ssh_key_from_agent(
@@ -79,197 +54,41 @@ where
                 panic!("This option must be unreachable.")
             }
         })
-        .transfer_progress(|progress| {
-            if progress.received_objects() == progress.total_objects() {
-                print!(
-                    "Resolving deltas {}/{}\r",
-                    progress.indexed_deltas(),
-                    progress.total_deltas()
-                );
-            } else {
-                print!(
-                    "Received {}/{} objects ({}) in {} bytes\r",
-                    progress.received_objects(),
-                    progress.total_objects(),
-                    progress.indexed_objects(),
-                    progress.received_bytes(),
-                );
-            }
-            io::stdout().flush().unwrap();
-            true
-        })
-        .sideband_progress(|text| {
-            let msg = String::from_utf8_lossy(text);
-            eprintln!("remote: {msg}");
-            true
-        })
         .push_transfer_progress(|current, total, bytes| {
-            trace!("{current}/{total} files sent \t{bytes} bytes");
-        })
-        .push_update_reference(|reference_name, status_msg| {
-            debug!("remote reference_name {reference_name}");
-            match status_msg {
-                None => {
-                    info!("successfully pushed");
-                    eprintln!("successfully pushed to {}", reference_name);
-                    Ok(())
-                }
-                Some(status) => {
-                    error!("failed to push: {}", status);
-                    Err(git2::Error::from_str(&format!(
-                        "failed to push to {}: {}",
-                        reference_name, status
-                    )))
-                }
-            }
+            trace!("{current},\t{total},\t{bytes}");
         });
-    callbacks
-}
-
-fn pull(
-    repo: &Repository,
-    remote: &mut git2::Remote,
-    remote_name: String,
-    use_sshagent: &bool,
-    ssh_key: Option<&PathBuf>,
-) -> Result<()> {
-    debug!("pull");
-    let callbacks = remote_callback(use_sshagent, ssh_key);
-    let mut fetchoptions = FetchOptions::new();
-    fetchoptions.remote_callbacks(callbacks);
-    let fetch_refspec: Vec<String> = remote
-        .refspecs()
-        .filter_map(|rs| match rs.direction() {
-            git2::Direction::Fetch => rs.str().map(|s| s.to_string()),
-            git2::Direction::Push => None,
-        })
-        .collect();
-    remote
-        .fetch(&fetch_refspec, Some(&mut fetchoptions), None)
-        .context("Failed to fetch (pull)")?;
-    let stats = remote.stats();
-    if stats.local_objects() > 0 {
-        println!(
-            "\rReceived {}/{} objects in {} bytes (used {} local objects)",
-            stats.indexed_objects(),
-            stats.total_objects(),
-            stats.received_bytes(),
-            stats.local_objects(),
-        );
-    } else {
-        println!(
-            "\rReceived {}/{} objects in {} bytes",
-            stats.indexed_objects(),
-            stats.total_objects(),
-            stats.received_bytes(),
-        );
-    }
-    let fetch_head = repo
-        .reference_to_annotated_commit(
-            &repo
-                .resolve_reference_from_short_name(&remote_name)
-                .context("failed to get reference from fetch refspec")?,
-        )
-        .context("failed to get annotated commit")?;
-    let (merge_analysis, merge_preference) = repo
-        .merge_analysis(&[&fetch_head])
-        .context("failed to do merge_analysis")?;
-
-    trace!("merge analysis: {:?}", merge_analysis);
-    trace!("merge preference: {:?}", merge_preference);
-    match merge_analysis {
-        ma if ma.is_up_to_date() => {
-            info!("HEAD is up to date. skip merging");
+    callbacks.push_update_reference(|reference_name, status_msg| {
+        debug!("remote reference_name {reference_name}");
+        match status_msg {
+            None => {
+                info!("successfully pushed");
+                eprintln!("successfully pushed to {}", reference_name);
+                Ok(())
+            }
+            Some(status) => {
+                error!("failed to push: {}", status);
+                Err(git2::Error::from_str(&format!(
+                    "failed to push to {}: {}",
+                    reference_name, status
+                )))
+            }
         }
-        ma if ma.is_fast_forward() => {
-            // https://github.com/rust-lang/git2-rs/blob/master/examples/pull.rs
-            info!("fast forward is available");
-            let mut ref_remote = repo
-                .find_reference(
-                    remote
-                        .default_branch()
-                        .context("failed to get remote default branch")?
-                        .as_str()
-                        .unwrap(),
-                )
-                .context("failed to get remote reference")?;
-            let name = match ref_remote.name() {
-                Some(s) => s.to_string(),
-                None => String::from_utf8_lossy(ref_remote.name_bytes()).to_string(),
-            };
-            let msg = format!("Fast-Forward: Setting {} to id: {}", name, fetch_head.id());
-            println!("{}", msg);
-            ref_remote
-                .set_target(fetch_head.id(), &msg)
-                .context("failed to set target")?;
-            repo.checkout_head(Some(CheckoutBuilder::default().force()))
-                .context("failed to checkout")?;
-        }
-        ma if ma.is_unborn() => {
-            warn!("HEAD is invalid (unborn)");
-            return Err(anyhow!(
-                "HEAD is invalid: merge_analysis: {:?}",
-                merge_analysis
-            ));
-        }
-        ma if ma.is_none() => {
-            error!("no merge is possible");
-            return Err(anyhow!("no merge is possible"));
-        }
-        ma if ma.is_normal() => {
-            error!("unable to fast-forward. manual merge is required");
-            return Err(anyhow!("unable to fast-forward. manual merge is required"));
-        }
-        _ma => {
-            error!(
-                "this code must not reachable: merge_analysis {:?}",
-                merge_analysis
-            );
-            return Err(anyhow!("must not be reachabel (uncovered merge_analysis)"));
-        }
-    }
-    Ok(())
-}
-
-fn push(
-    repo: &Repository,
-    remote: &mut git2::Remote,
-    use_sshagent: &bool,
-    ssh_key: Option<&PathBuf>,
-) -> Result<()> {
-    debug!("push");
-    let callbacks = remote_callback(&use_sshagent, ssh_key);
+    });
     let mut push_options = PushOptions::new();
     push_options.remote_callbacks(callbacks);
-    let num_push_refspecs = remote
-        .refspecs()
-        .filter(|rs| rs.direction() == git2::Direction::Push)
-        .count();
-    if num_push_refspecs > 1 {
-        warn!("more than one push refspecs are configured");
-        warn!("using the first one");
+    let mut remote = repo.find_remote(&remote_name)?;
+    trace!("remote: {:?}", remote.name());
+    if remote.refspecs().len() != 1 {
+        warn!("multiple refspecs found");
     }
-    let head = repo.head().context("Failed to get HEAD")?;
-    if num_push_refspecs >= 1 {
-        trace!("using push refspec");
-        let push_refspec = remote
-            .refspecs()
-            .filter_map(|rs| match rs.direction() {
-                git2::Direction::Fetch => None,
-                git2::Direction::Push => Some(rs),
-            })
-            .next()
-            .expect("this must be unreachabe")
-            .str()
-            .context("failed to get valid utf8 push refspec")?
-            .to_string();
-        remote.push(&[push_refspec.as_str()] as &[&str], Some(&mut push_options))?;
-    } else {
-        trace!("using head as push refspec");
-        trace!("head is branch: {:?}", head.is_branch());
-        trace!("head is remote: {:?}", head.is_remote());
-        let push_refspec = head.name().context("failed to get head name")?;
-        remote.push(&[push_refspec] as &[&str], Some(&mut push_options))?;
-    };
+    trace!("refspec: {:?}", remote.get_refspec(0).unwrap().str());
+    trace!("refspec: {:?}", remote.get_refspec(0).unwrap().direction());
+    trace!("refspec: {:?}", repo.head().unwrap().name());
+    trace!("head is branch: {:?}", repo.head().unwrap().is_branch());
+    trace!("head is remote: {:?}", repo.head().unwrap().is_remote());
+    remote.push(
+        &[repo.head().unwrap().name().unwrap()] as &[&str],
+        Some(&mut push_options),
+    )?;
     Ok(())
 }
diff --git a/tests/cli.rs b/tests/cli.rs
index b282410..44e93cd 100644
--- a/tests/cli.rs
+++ b/tests/cli.rs
@@ -2,7 +2,6 @@ mod integrated_test {
     use std::{
         fs::{self, DirBuilder, File},
         io::{self, BufWriter, Write},
-        path,
     };
 
     use anyhow::{anyhow, Context, Ok, Result};
@@ -73,16 +72,6 @@ mod integrated_test {
         Ok(())
     }
 
-    fn run_sync_cmd(config_dir: &path::Path) -> Result<()> {
-        Command::cargo_bin("xdbm")?
-            .arg("-c")
-            .arg(config_dir)
-            .args(["sync", "-vvvv"])
-            .assert()
-            .success();
-        Ok(())
-    }
-
     #[test]
     fn single_device() -> Result<()> {
         let config_dir = assert_fs::TempDir::new()?;
@@ -391,8 +380,16 @@ mod integrated_test {
             std::fs::read_to_string(config_dir_1.join("storages.yml"))?.contains("parent: gdrive1")
         );
 
-        run_sync_cmd(&config_dir_1)?;
-        run_sync_cmd(&config_dir_2)?;
+        std::process::Command::new("git")
+            .arg("push")
+            .current_dir(&config_dir_1)
+            .assert()
+            .success();
+        std::process::Command::new("git")
+            .arg("pull")
+            .current_dir(&config_dir_2)
+            .assert()
+            .success();
 
         // bind
         //
@@ -606,8 +603,16 @@ mod integrated_test {
                     .and(predicate::str::contains("foodoc").not()),
             );
 
-        run_sync_cmd(&config_dir_2)?;
-        run_sync_cmd(&config_dir_1)?;
+        std::process::Command::new("git")
+            .arg("push")
+            .current_dir(&config_dir_2)
+            .assert()
+            .success();
+        std::process::Command::new("git")
+            .arg("pull")
+            .current_dir(&config_dir_1)
+            .assert()
+            .success();
 
         // bind
         //
@@ -722,8 +727,16 @@ mod integrated_test {
             .assert()
             .success();
 
-        run_sync_cmd(&config_dir_1)?;
-        run_sync_cmd(&config_dir_2)?;
+        std::process::Command::new("git")
+            .arg("push")
+            .current_dir(&config_dir_1)
+            .assert()
+            .success();
+        std::process::Command::new("git")
+            .arg("pull")
+            .current_dir(&config_dir_2)
+            .assert()
+            .success();
 
         // backup add
         //