feat: Adds Git State module for showing "REBASING 2/3", etc. (#276)

- Adds the git_state module.
- Adds git_state to the default prompt order
- Updates the documentation to describe the git_state module

9 files changed, 396 insertions, 13 deletions

diff --git a/docs/config/README.md b/docs/config/README.md
index 944545246..702d21a51 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -72,6 +72,7 @@ default_prompt_order = [
     "hostname",
     "directory",
     "git_branch",
+    "git_state",
     "git_status",
     "package",
     "nodejs",
@@ -79,6 +80,7 @@ default_prompt_order = [
     "rust",
     "python",
     "golang",
+    "nix_shell",
     "cmd_duration",
     "line_break",
     "jobs",
@@ -230,6 +232,37 @@ truncation_length = "4"
 truncation_symbol = ""
 ```
 
+## Git State
+
+The `git_state` module will show in directories which are part of a git
+repository, and where there is an operation in progress, such as: _REBASING_,
+_BISECTING_, etc. If there is progress information (e.g., REBASING 3/10),
+that information will be shown too.
+
+### Options
+
+| Variable           | Default            | Description                                                                                                      |
+| ------------------ | ------------------ | ---------------------------------------------------------------------------------------------------------------- |
+| `rebase`           | `"REBASING"`       | The text displayed when a `rebase` is in progress.                                                               |
+| `merge`            | `"MERGING"`        | The text displayed when a `merge` is in progress.                                                                |
+| `revert`           | `"REVERTING"`      | The text displayed when a `revert` is in progress.                                                               |
+| `cherry_pick`      | `"CHERRY-PICKING"` | The text displayed when a `cherry-pick` is in progress.                                                          |
+| `bisect`           | `"BISECTING"`      | The text displayed when a `bisect` is in progress.                                                               |
+| `am`               | `"AM"`             | The text displayed when an `apply-mailbox` (`git am`) is in progress.                                            |
+| `am_or_rebase`     | `"AM/REBASE"`      | The text displayed when an ambiguous `apply-mailbox` or `rebase` is in progress.                                 |
+| `progress_divider` | `"/"`              | The symbol or text which will separate the current and total progress amounts. (e.g., `" of "`, for `"3 of 10"`) |
+| `disabled`         | `false`            | Disables the `git_state` module.                                                                                 |
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[git_state]
+progress_divider = " of "
+cherry_pick = "🍒 PICKING"
+```
+
 ## Git Status
 
 The `git_status` module shows symbols representing the state of the repo in your
@@ -276,12 +309,12 @@ The `hostname` module shows the system hostname.
 
 ### Options
 
-| Variable     | Default | Description                                             |
-| ------------ | ------- | ------------------------------------------------------- |
-| `ssh_only`   | `true`  | Only show hostname when connected to an SSH session.    |
-| `prefix`     | `""`    | Prefix to display immediately before the hostname.      |
-| `suffix`     | `""`    | Suffix to display immediately after the hostname.       |
-| `disabled`   | `false` | Disables the `hostname` module.                         |
+| Variable   | Default | Description                                          |
+| ---------- | ------- | ---------------------------------------------------- |
+| `ssh_only` | `true`  | Only show hostname when connected to an SSH session. |
+| `prefix`   | `""`    | Prefix to display immediately before the hostname.   |
+| `suffix`   | `""`    | Suffix to display immediately after the hostname.    |
+| `disabled` | `false` | Disables the `hostname` module.                      |
 
 ### Example
 
@@ -378,10 +411,10 @@ The module will be shown if any of the following conditions are met:
 
 ### Options
 
-| Variable   | Default | Description                 |
-| ---------- | ------- | --------------------------- |
-| `symbol`    | `"💎 "`  | The symbol used before displaying the version of Ruby. |
-| `disabled` | `false` | Disables the `ruby` module. |
+| Variable   | Default | Description                                            |
+| ---------- | ------- | ------------------------------------------------------ |
+| `symbol`   | `"💎 "` | The symbol used before displaying the version of Ruby. |
+| `disabled` | `false` | Disables the `ruby` module.                            |
 
 ### Example
 
diff --git a/src/module.rs b/src/module.rs
index 28c309c6d..ab1783e4f 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -12,6 +12,7 @@ pub const ALL_MODULES: &[&str] = &[
     "cmd_duration",
     "directory",
     "git_branch",
+    "git_state",
     "git_status",
     "golang",
     "hostname",
diff --git a/src/modules/git_state.rs b/src/modules/git_state.rs
new file mode 100644
index 000000000..55f3d4c11
--- /dev/null
+++ b/src/modules/git_state.rs
@@ -0,0 +1,166 @@
+use ansi_term::Color;
+use git2::{Repository, RepositoryState};
+use std::path::Path;
+
+use super::{Context, Module};
+
+/// Creates a module with the state of the git repository at the current directory
+///
+/// During a git operation it will show: REBASING, BISECTING, MERGING, etc.
+/// If the progress information is available (e.g. rebasing 3/10), it will show that too.
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("git_state")?;
+
+    let repo_root = context.repo_root.as_ref()?;
+    let mut repository = Repository::open(repo_root).ok()?;
+    let state_description = get_state_description(&mut repository);
+
+    if let StateDescription::Clean = state_description {
+        return None;
+    }
+
+    module.get_prefix().set_value("(");
+    module.get_suffix().set_value(") ");
+    module.set_style(Color::Yellow.bold());
+
+    let label = match state_description {
+        StateDescription::Label(label) => label,
+        StateDescription::LabelAndProgress(label, _) => label,
+        // Should only be possible if you've added a new variant to StateDescription
+        _ => panic!("Expected to have a label at this point in the control flow."),
+    };
+
+    module.new_segment(label.segment_name, label.message_default);
+
+    if let StateDescription::LabelAndProgress(_, progress) = state_description {
+        module.new_segment("progress_current", &format!(" {}", progress.current));
+        module.new_segment("progress_divider", "/");
+        module.new_segment("progress_total", &format!("{}", progress.total));
+    }
+
+    Some(module)
+}
+
+static MERGE_LABEL: StateLabel = StateLabel {
+    segment_name: "merge",
+    message_default: "MERGING",
+};
+
+static REVERT_LABEL: StateLabel = StateLabel {
+    segment_name: "revert",
+    message_default: "REVERTING",
+};
+
+static CHERRY_LABEL: StateLabel = StateLabel {
+    segment_name: "cherry_pick",
+    message_default: "CHERRY-PICKING",
+};
+
+static BISECT_LABEL: StateLabel = StateLabel {
+    segment_name: "bisect",
+    message_default: "BISECTING",
+};
+
+static AM_LABEL: StateLabel = StateLabel {
+    segment_name: "am",
+    message_default: "AM",
+};
+
+static REBASE_LABEL: StateLabel = StateLabel {
+    segment_name: "rebase",
+    message_default: "REBASING",
+};
+
+static AM_OR_REBASE_LABEL: StateLabel = StateLabel {
+    segment_name: "am_or_rebase",
+    message_default: "AM/REBASE",
+};
+
+fn get_state_description(repository: &mut Repository) -> StateDescription {
+    match repository.state() {
+        RepositoryState::Clean => StateDescription::Clean,
+        RepositoryState::Merge => StateDescription::Label(&MERGE_LABEL),
+        RepositoryState::Revert => StateDescription::Label(&REVERT_LABEL),
+        RepositoryState::RevertSequence => StateDescription::Label(&REVERT_LABEL),
+        RepositoryState::CherryPick => StateDescription::Label(&CHERRY_LABEL),
+        RepositoryState::CherryPickSequence => StateDescription::Label(&CHERRY_LABEL),
+        RepositoryState::Bisect => StateDescription::Label(&BISECT_LABEL),
+        RepositoryState::ApplyMailbox => StateDescription::Label(&AM_LABEL),
+        RepositoryState::ApplyMailboxOrRebase => StateDescription::Label(&AM_OR_REBASE_LABEL),
+        RepositoryState::Rebase => describe_rebase(repository),
+        RepositoryState::RebaseInteractive => describe_rebase(repository),
+        RepositoryState::RebaseMerge => describe_rebase(repository),
+    }
+}
+
+fn describe_rebase(repository: &mut Repository) -> StateDescription {
+    /*
+     *  Sadly, libgit2 seems to have some issues with reading the state of
+     *  interactive rebases. So, instead, we'll poke a few of the .git files
+     *  ourselves. This might be worth re-visiting this in the future...
+     *
+     *  The following is based heavily on: https://github.com/magicmonty/bash-git-prompt
+     */
+
+    let just_label = StateDescription::Label(&REBASE_LABEL);
+
+    let dot_git = repository
+        .workdir()
+        .and_then(|d| Some(d.join(Path::new(".git"))));
+
+    let dot_git = match dot_git {
+        None => {
+            // We didn't find the .git directory.
+            // Something very odd is going on. We'll just back away slowly.
+            return just_label;
+        }
+        Some(path) => path,
+    };
+
+    let has_path = |relative_path: &str| {
+        let path = dot_git.join(Path::new(relative_path));
+        path.exists()
+    };
+
+    let file_to_usize = |relative_path: &str| {
+        let path = dot_git.join(Path::new(relative_path));
+        let contents = crate::utils::read_file(path).ok()?;
+        let quantity = contents.trim().parse::<usize>().ok()?;
+        Some(quantity)
+    };
+
+    let paths_to_progress = |current_path: &str, total_path: &str| {
+        let current = file_to_usize(current_path)?;
+        let total = file_to_usize(total_path)?;
+        Some(StateProgress { current, total })
+    };
+
+    let progress = if has_path("rebase-merge") {
+        paths_to_progress("rebase-merge/msgnum", "rebase-merge/end")
+    } else if has_path("rebase-apply") {
+        paths_to_progress("rebase-apply/next", "rebase-apply/last")
+    } else {
+        None
+    };
+
+    match progress {
+        None => just_label,
+        Some(progress) => StateDescription::LabelAndProgress(&REBASE_LABEL, progress),
+    }
+}
+
+enum StateDescription {
+    Clean,
+    Label(&'static StateLabel),
+    LabelAndProgress(&'static StateLabel, StateProgress),
+}
+
+struct StateLabel {
+    segment_name: &'static str,
+    message_default: &'static str,
+}
+
+struct StateProgress {
+    current: usize,
+    total: usize,
+}
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index 23d82601f..83a7d1c40 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -3,6 +3,7 @@ mod character;
 mod cmd_duration;
 mod directory;
 mod git_branch;
+mod git_state;
 mod git_status;
 mod golang;
 mod hostname;
@@ -34,6 +35,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         "line_break" => line_break::module(context),
         "package" => package::module(context),
         "git_branch" => git_branch::module(context),
+        "git_state" => git_state::module(context),
         "git_status" => git_status::module(context),
         "username" => username::module(context),
         #[cfg(feature = "battery")]
diff --git a/src/print.rs b/src/print.rs
index 74997b26d..1ea1648ff 100644
--- a/src/print.rs
+++ b/src/print.rs
@@ -16,6 +16,7 @@ const DEFAULT_PROMPT_ORDER: &[&str] = &[
     "hostname",
     "directory",
     "git_branch",
+    "git_state",
     "git_status",
     "package",
     "nodejs",
diff --git a/src/utils.rs b/src/utils.rs
index 4a0337ae6..c873f45aa 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,8 +1,9 @@
 use std::fs::File;
 use std::io::{Read, Result};
+use std::path::Path;
 
 /// Return the string contents of a file
-pub fn read_file(file_name: &str) -> Result<String> {
+pub fn read_file<P: AsRef<Path>>(file_name: P) -> Result<String> {
     let mut file = File::open(file_name)?;
     let mut data = String::new();
 
diff --git a/tests/testsuite/common.rs b/tests/testsuite/common.rs
index 0f611a209..6698a1d94 100644
--- a/tests/testsuite/common.rs
+++ b/tests/testsuite/common.rs
@@ -2,7 +2,7 @@ use lazy_static::lazy_static;
 use std::io::prelude::*;
 use std::path::{Path, PathBuf};
 use std::process::Command;
-use std::{env, io, process};
+use std::{env, fs, io, process};
 
 lazy_static! {
     static ref MANIFEST_DIR: &'static Path = Path::new(env!("CARGO_MANIFEST_DIR"));
@@ -25,7 +25,8 @@ pub fn render_prompt() -> process::Command {
 
 /// Render a specific starship module by name
 pub fn render_module(module_name: &str) -> process::Command {
-    let mut command = process::Command::new("./target/debug/starship");
+    let binary = fs::canonicalize("./target/debug/starship").unwrap();
+    let mut command = process::Command::new(binary);
 
     command
         .arg("module")
diff --git a/tests/testsuite/git_state.rs b/tests/testsuite/git_state.rs
new file mode 100644
index 000000000..2de7d5029
--- /dev/null
+++ b/tests/testsuite/git_state.rs
@@ -0,0 +1,177 @@
+use super::common;
+use std::ffi::OsStr;
+use std::fs::OpenOptions;
+use std::io::{self, Error, ErrorKind, Write};
+use std::process::{Command, Stdio};
+
+#[test]
+#[ignore]
+fn shows_rebasing() -> io::Result<()> {
+    let repo_dir = create_repo_with_conflict()?;
+    let path = path_str(&repo_dir)?;
+
+    run_git_cmd(&["rebase", "other-branch"], Some(path), false)?;
+
+    let output = common::render_module("git_state")
+        .current_dir(path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+    assert!(text.contains("REBASING 1/1"));
+
+    Ok(())
+}
+
+#[test]
+#[ignore]
+fn shows_merging() -> io::Result<()> {
+    let repo_dir = create_repo_with_conflict()?;
+    let path = path_str(&repo_dir)?;
+
+    run_git_cmd(&["merge", "other-branch"], Some(path), false)?;
+
+    let output = common::render_module("git_state")
+        .current_dir(path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+    assert!(text.contains("MERGING"));
+
+    Ok(())
+}
+
+#[test]
+#[ignore]
+fn shows_cherry_picking() -> io::Result<()> {
+    let repo_dir = create_repo_with_conflict()?;
+    let path = path_str(&repo_dir)?;
+
+    run_git_cmd(&["cherry-pick", "other-branch"], Some(path), false)?;
+
+    let output = common::render_module("git_state")
+        .current_dir(path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+    assert!(text.contains("CHERRY-PICKING"));
+
+    Ok(())
+}
+
+#[test]
+#[ignore]
+fn shows_bisecting() -> io::Result<()> {
+    let repo_dir = create_repo_with_conflict()?;
+    let path = path_str(&repo_dir)?;
+
+    run_git_cmd(&["bisect", "start"], Some(path), false)?;
+
+    let output = common::render_module("git_state")
+        .current_dir(path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+    assert!(text.contains("BISECTING"));
+
+    Ok(())
+}
+
+#[test]
+#[ignore]
+fn shows_reverting() -> io::Result<()> {
+    let repo_dir = create_repo_with_conflict()?;
+    let path = path_str(&repo_dir)?;
+
+    run_git_cmd(&["revert", "--no-commit", "HEAD~1"], Some(path), false)?;
+
+    let output = common::render_module("git_state")
+        .current_dir(path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+    assert!(text.contains("REVERTING"));
+
+    Ok(())
+}
+
+fn run_git_cmd<A, S>(args: A, dir: Option<&str>, expect_ok: bool) -> io::Result<()>
+where
+    A: IntoIterator<Item = S>,
+    S: AsRef<OsStr>,
+{
+    let mut command = Command::new("git");
+    command
+        .args(args)
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .stdin(Stdio::null());
+
+    if let Some(dir) = dir {
+        command.current_dir(dir);
+    }
+
+    let status = command.status()?;
+
+    if expect_ok && !status.success() {
+        Err(Error::from(ErrorKind::Other))
+    } else {
+        Ok(())
+    }
+}
+
+fn create_repo_with_conflict() -> io::Result<tempfile::TempDir> {
+    let repo_dir = common::new_tempdir()?;
+    let path = path_str(&repo_dir)?;
+    let conflicted_file = repo_dir.path().join("the_file");
+
+    let write_file = |text: &str| {
+        let mut file = OpenOptions::new()
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(&conflicted_file)?;
+        write!(file, "{}", text)
+    };
+
+    // Initialise a new git repo
+    run_git_cmd(&["init", "--quiet", path], None, true)?;
+
+    // Set local author info
+    run_git_cmd(
+        &["config", "--local", "user.email", "starship@example.com"],
+        Some(path),
+        true,
+    )?;
+    run_git_cmd(
+        &["config", "--local", "user.name", "starship"],
+        Some(path),
+        true,
+    )?;
+
+    // Write a file on master and commit it
+    write_file("Version A")?;
+    run_git_cmd(&["add", "the_file"], Some(path), true)?;
+    run_git_cmd(&["commit", "--message", "Commit A"], Some(path), true)?;
+
+    // Switch to another branch, and commit a change to the file
+    run_git_cmd(&["checkout", "-b", "other-branch"], Some(path), true)?;
+    write_file("Version B")?;
+    run_git_cmd(
+        &["commit", "--all", "--message", "Commit B"],
+        Some(path),
+        true,
+    )?;
+
+    // Switch back to master, and commit a third change to the file
+    run_git_cmd(&["checkout", "master"], Some(path), true)?;
+    write_file("Version C")?;
+    run_git_cmd(
+        &["commit", "--all", "--message", "Commit C"],
+        Some(path),
+        true,
+    )?;
+
+    Ok(repo_dir)
+}
+
+fn path_str(repo_dir: &tempfile::TempDir) -> io::Result<&str> {
+    repo_dir
+        .path()
+        .to_str()
+        .ok_or_else(|| Error::from(ErrorKind::Other))
+}
diff --git a/tests/testsuite/main.rs b/tests/testsuite/main.rs
index 82da9cccf..bf64f3099 100644
--- a/tests/testsuite/main.rs
+++ b/tests/testsuite/main.rs
@@ -4,6 +4,7 @@ mod common;
 mod configuration;
 mod directory;
 mod git_branch;
+mod git_state;
 mod git_status;
 mod golang;
 mod hostname;