Add `branch` subcommand for starting a new branch

Cargo.lock

@@ -168,6 +168,16 @@ dependencies = [
  "cfg-if 1.0.0",
 ]
 
+[[package]]
+name = "eyre"
+version = "0.6.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c2b6b5a29c02cdc822728b7d7b8ae1bab3e3b05d44522770ddd49722eeac7eb"
+dependencies = [
+ "indenter",
+ "once_cell",
+]
+
 [[package]]
 name = "fastrand"
 version = "1.8.0"
@@ -326,12 +336,14 @@ dependencies = [
  "console",
  "dialoguer",
  "dotenv",
+ "eyre",
  "futures",
  "git2",
  "petgraph",
  "regex",
  "reqwest",
  "serde",
+ "serde_json",
  "tokio",
 ]
 
@@ -465,6 +477,12 @@ dependencies = [
  "unicode-normalization",
 ]
 
+[[package]]
+name = "indenter"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce23b50ad8242c51a442f3ff322d56b02f08852c77e4c0b4d3fd684abc89c683"
+
 [[package]]
 name = "indexmap"
 version = "1.9.2"

Cargo.toml

@@ -23,4 +23,6 @@ git2 = "0.13"
 dialoguer = "0.6.2"
 clap = "2.33"
 console = "0.11"
-dotenv = "0.15"
+dotenv = "0.15"
+eyre = "0.6.8"
+serde_json = "1.0.89"

src/api/search.rs

@@ -36,7 +36,7 @@ pub async fn fetch_reviews_for_pull_request(
 pub async fn fetch_pull_requests_matching(
     pattern: &str,
     credentials: &Credentials,
-) -> Result<Vec<PullRequest>, Box<dyn Error>> {
+) -> eyre::Result<Vec<PullRequest>> {
     let client = reqwest::Client::new();
 
     let request = api::base_request(
@@ -75,8 +75,7 @@ pub async fn fetch_matching_pull_requests_from_repository(
     pattern: &str,
     repository: &str,
     credentials: &Credentials,
-) -> Result<Vec<PullRequest>, Box<dyn Error>> {
-
+) -> eyre::Result<Vec<PullRequest>> {
     let client = reqwest::Client::new();
 
     let request = api::base_request(

src/filepersist.rs

@@ -0,0 +1,52 @@
+use eyre::Context;
+use git2::Repository;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Clone, Debug, Serialize, Deserialize, Default)]
+pub struct BranchPersistenceData {
+    pub base_branch: Option<String>,
+    pub base_commit: Option<(String, u64)>,
+    pub stack_tag: Option<String>,
+}
+
+pub fn find_persistence_path(repo: &Repository) -> eyre::Result<PathBuf> {
+    let persist_path = repo.path().join("git-stack");
+    if !persist_path.exists() {
+        std::fs::create_dir(&persist_path).context("Failed to create persistence path")?;
+    }
+    Ok(persist_path)
+}
+
+pub fn persistence_path_for_branch(repo: &Repository, branch: &str) -> eyre::Result<PathBuf> {
+    Ok(find_persistence_path(repo)?.join(branch))
+}
+
+pub fn load_persistence_data_for_branch(
+    repo: &Repository,
+    branch: &str,
+) -> eyre::Result<BranchPersistenceData> {
+    let path = persistence_path_for_branch(repo, branch)?;
+    if !path.exists() {
+        return Ok(Default::default());
+    }
+    let content = std::fs::read(&path).with_context(|| format!("failed to read {path:?}"))?;
+    Ok(serde_json::from_slice::<BranchPersistenceData>(&content)
+        .with_context(|| format!("failed to deserialise {path:?}"))?)
+}
+
+pub fn save_persistence_data_for_branch(
+    repo: &Repository,
+    branch: &str,
+    data: &BranchPersistenceData,
+) -> eyre::Result<()> {
+    let path = persistence_path_for_branch(repo, branch)?;
+    let parent = path.parent().unwrap();
+    if !parent.exists() {
+        std::fs::create_dir_all(parent)
+            .with_context(|| format!("failed to create dirs {:?}", parent))?;
+    }
+    let json = serde_json::to_vec(data)?;
+    std::fs::write(&path, json).with_context(|| format!("failed to write {path:?}"))?;
+    Ok(())
+}

src/git.rs

@@ -4,7 +4,6 @@ use crate::util::loop_until_confirm;
 use git2::build::CheckoutBuilder;
 use git2::{CherrypickOptions, Commit, Index, Oid, Repository, Revwalk, Sort};
 
-use std::error::Error;
 use tokio::process::Command;
 
 fn remote_ref(remote: &str, git_ref: &str) -> String {
@@ -149,7 +148,7 @@ pub async fn perform_rebase(
     remote: &str,
     boundary: Option<&str>,
     ci: bool,
-) -> Result<(), Box<dyn Error>> {
+) -> eyre::Result<()> {
     let deps = deps
         .iter()
         .filter(|(dep, _)| *dep.state() == PullRequestStatus::Open)

src/lib.rs

@@ -1,4 +1,5 @@
 pub mod api;
+pub mod filepersist;
 pub mod git;
 pub mod graph;
 pub mod markdown;

src/main.rs

@@ -1,12 +1,16 @@
 use clap::{App, AppSettings, Arg, ArgMatches, SubCommand};
 use console::style;
+use eyre::{bail, Context, ContextCompat};
 use git2::Repository;
 use regex::Regex;
 use std::env;
-use std::error::Error;
 use std::rc::Rc;
+use std::time::{SystemTime, UNIX_EPOCH};
 
 use git_stack::api::PullRequest;
+use git_stack::filepersist::{
+    load_persistence_data_for_branch, save_persistence_data_for_branch, BranchPersistenceData,
+};
 use git_stack::graph::FlatDep;
 use git_stack::util::loop_until_confirm;
 use git_stack::Credentials;
@@ -93,6 +97,22 @@ fn clap<'a, 'b>() -> App<'a, 'b> {
         .arg(exclude.clone())
         .arg(identifier.clone());
 
+    let branch = SubCommand::with_name("branch")
+        .about(
+            "Create a new branch that is part of a stack."
+        )
+        .setting(AppSettings::ArgRequiredElseHelp)
+        .arg(Arg::with_name("name")
+            .help("Branch name")
+            .required(true)
+            .takes_value(true))
+        .arg(Arg::with_name("identifier")
+            .required(false)
+            .long("identifier")
+            .short("i")
+            .takes_value(true)
+            .help("Name of the stack (overrides current stack; mainly useful for starting a stack)"));
+
     let app = App::new("git-stack")
         .setting(AppSettings::SubcommandRequiredElseHelp)
         .setting(AppSettings::DisableVersion)
@@ -101,7 +121,8 @@ fn clap<'a, 'b>() -> App<'a, 'b> {
         .subcommand(annotate)
         .subcommand(log)
         .subcommand(rebase)
-        .subcommand(autorebase);
+        .subcommand(autorebase)
+        .subcommand(branch);
 
     app
 }
@@ -110,7 +131,7 @@ async fn build_pr_stack(
     pattern: &str,
     credentials: &Credentials,
     exclude: Vec<String>,
-) -> Result<FlatDep, Box<dyn Error>> {
+) -> eyre::Result<FlatDep> {
     let prs = api::search::fetch_pull_requests_matching(pattern, &credentials).await?;
 
     let prs = prs
@@ -128,7 +149,7 @@ async fn build_pr_stack_for_repo(
     repository: &str,
     credentials: &Credentials,
     exclude: Vec<String>,
-) -> Result<FlatDep, Box<dyn Error>> {
+) -> eyre::Result<FlatDep> {
     let prs = api::search::fetch_matching_pull_requests_from_repository(
         pattern,
         repository,
@@ -162,7 +183,7 @@ fn remove_title_prefixes(title: String, prefix: &str) -> String {
 }
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn Error>> {
+async fn main() -> eyre::Result<()> {
     dotenv::from_filename(".gh-stack.env").ok();
 
     let token = env::var("GHSTACK_OAUTH_TOKEN").expect("You didn't pass `GHSTACK_OAUTH_TOKEN`");
@@ -171,6 +192,8 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let credentials = Credentials::new(&token);
     let matches = clap().get_matches();
 
+    let repo = Repository::open(".").context("Couldn't open git repository; are you in one?")?;
+
     match matches.subcommand() {
         ("annotate", Some(m)) => {
             let identifier = m.value_of("identifier").unwrap();
@@ -306,6 +329,69 @@ async fn main() -> Result<(), Box<dyn Error>> {
             println!("All done!");
         }
 
+        ("branch", Some(m)) => {
+            let head = repo.head()?;
+            if !head.is_branch() {
+                bail!("Current HEAD isn't a branch.");
+            }
+            let current_branch = head
+                .shorthand()
+                .context("No name for the current reference")?;
+            let current_commit = head.peel_to_commit().context("Can't peel to commit")?;
+
+            let head_stack_info = load_persistence_data_for_branch(&repo, current_branch)
+                .context("Failed to load branch persistence data for current branch")?;
+
+            println!(
+                "Current branch is {current_branch} @ {}.",
+                current_commit.id()
+            );
+
+            let branch_name = m.value_of("name").unwrap();
+
+            let new_stack_identifier = match head_stack_info.stack_tag {
+                None => {
+                    println!("{current_branch} is not part of a stack.");
+                    match m.value_of("identifier") {
+                        None => {
+                            bail!("Current branch not part of a stack and a stack identifier was not specified with -i!");
+                        }
+                        Some(ident) => ident.to_owned(),
+                    }
+                }
+                Some(cur_stack) => {
+                    println!("{current_branch} is part of the [{cur_stack}] stack.");
+                    match m.value_of("identifier") {
+                        None => cur_stack,
+                        Some(_) => {
+                            bail!("Current branch is part of a stack but a stack identifier was specified with -i!");
+                        }
+                    }
+                }
+            };
+
+            let new_branch = repo
+                .branch(branch_name, &current_commit, false)
+                .context("Can't create branch")?;
+            repo.set_head(new_branch.into_reference().name().unwrap())
+                .context("Couldn't switch to new branch")?;
+            save_persistence_data_for_branch(
+                &repo,
+                branch_name,
+                &BranchPersistenceData {
+                    base_branch: Some(current_branch.to_owned()),
+                    base_commit: Some((
+                        current_commit.id().to_string(),
+                        SystemTime::now()
+                            .duration_since(UNIX_EPOCH)
+                            .unwrap()
+                            .as_secs(),
+                    )),
+                    stack_tag: Some(new_stack_identifier),
+                },
+            )?;
+        }
+
         (_, _) => panic!("Invalid subcommand."),
     }
 

src/persist.rs

@@ -1,6 +1,5 @@
 use futures::future::join_all;
 use regex::Regex;
-use std::error::Error;
 
 use crate::api::pull_request;
 use crate::graph::FlatDep;
@@ -45,7 +44,7 @@ pub async fn persist(
     table: &str,
     c: &Credentials,
     prefix: &str,
-) -> Result<(), Box<dyn Error>> {
+) -> eyre::Result<()> {
     let futures = prs.iter().map(|(pr, _)| {
         let body = table.replace(&pr.title()[..], &format!("👉 {}", pr.title())[..]);
         let body = remove_title_prefixes(body, prefix);