From 791dd666430fe0586c7db75b352487a72d3789e7 Mon Sep 17 00:00:00 2001
From: Sebastian Thiel <sebastian.thiel@icloud.com>
Date: Wed, 31 Aug 2022 10:07:59 +0800
Subject: [PATCH] A basic implementation of rev-list without anything fancy

---
 README.md                                     |  1 +
 gitoxide-core/src/repository/revision/list.rs | 27 +++++++++++++++++++
 gitoxide-core/src/repository/revision/mod.rs  |  4 ++-
 .../repository/revision/previous_branches.rs  |  6 ++++-
 src/plumbing/main.rs                          | 10 +++++++
 src/plumbing/options.rs                       |  3 +++
 6 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 gitoxide-core/src/repository/revision/list.rs

diff --git a/README.md b/README.md
index 9f740c4eaf1..4df931cd798 100644
--- a/README.md
+++ b/README.md
@@ -42,6 +42,7 @@ Please see _'Development Status'_ for a listing of all crates and their capabili
     * **mailmap**
         * [x] **entries** - display all entries of the aggregated mailmap git would use for substitution
     * **revision**
+        * [x] **list** - list plain revision hashes from a starting point, similar to a very simple version of `git rev-list`.
         * [x] **explain** - show what would be done while parsing a revision specification like `HEAD~1`
         * [x] **resolve** - show which objects a revspec resolves to, similar to `git rev-parse` but faster and with much better error handling
         * [x] **previous-branches** - list all previously checked out branches, powered by the ref-log.
diff --git a/gitoxide-core/src/repository/revision/list.rs b/gitoxide-core/src/repository/revision/list.rs
new file mode 100644
index 00000000000..f3f34f90cd9
--- /dev/null
+++ b/gitoxide-core/src/repository/revision/list.rs
@@ -0,0 +1,27 @@
+use anyhow::{bail, Context};
+use git_repository as git;
+use std::ffi::OsString;
+
+use crate::OutputFormat;
+
+pub fn list(
+    mut repo: git::Repository,
+    spec: OsString,
+    mut out: impl std::io::Write,
+    format: OutputFormat,
+) -> anyhow::Result<()> {
+    if format != OutputFormat::Human {
+        bail!("Only human output is currently supported");
+    }
+    repo.object_cache_size_if_unset(4 * 1024 * 1024);
+
+    let spec = git::path::os_str_into_bstr(&spec)?;
+    let id = repo
+        .rev_parse(spec)?
+        .single()
+        .context("Only single revisions are currently supported")?;
+    for commit in id.ancestors().all()? {
+        writeln!(out, "{}", commit?.to_hex())?;
+    }
+    Ok(())
+}
diff --git a/gitoxide-core/src/repository/revision/mod.rs b/gitoxide-core/src/repository/revision/mod.rs
index 3e8937e29f2..5e5dda98af5 100644
--- a/gitoxide-core/src/repository/revision/mod.rs
+++ b/gitoxide-core/src/repository/revision/mod.rs
@@ -1,3 +1,5 @@
+mod list;
+pub use list::list;
 mod explain;
 pub use explain::explain;
 
@@ -5,4 +7,4 @@ pub mod resolve;
 pub use resolve::function::resolve;
 
 mod previous_branches;
-pub use previous_branches::function as previous_branches;
+pub use previous_branches::previous_branches;
diff --git a/gitoxide-core/src/repository/revision/previous_branches.rs b/gitoxide-core/src/repository/revision/previous_branches.rs
index 1cd39aa6e85..b22e6398eee 100644
--- a/gitoxide-core/src/repository/revision/previous_branches.rs
+++ b/gitoxide-core/src/repository/revision/previous_branches.rs
@@ -3,7 +3,11 @@ use git_repository as git;
 
 use crate::OutputFormat;
 
-pub fn function(repo: git::Repository, mut out: impl std::io::Write, format: OutputFormat) -> anyhow::Result<()> {
+pub fn previous_branches(
+    repo: git::Repository,
+    mut out: impl std::io::Write,
+    format: OutputFormat,
+) -> anyhow::Result<()> {
     let branches = repo
         .head()?
         .prior_checked_out_branches()?
diff --git a/src/plumbing/main.rs b/src/plumbing/main.rs
index b3d51c10f4c..9d3a021880a 100644
--- a/src/plumbing/main.rs
+++ b/src/plumbing/main.rs
@@ -534,6 +534,16 @@ pub fn main() -> Result<()> {
             },
         ),
         Subcommands::Revision(cmd) => match cmd {
+            revision::Subcommands::List { spec } => prepare_and_run(
+                "revision-list",
+                verbose,
+                progress,
+                progress_keep_open,
+                None,
+                move |_progress, out, _err| {
+                    core::repository::revision::list(repository(Mode::Lenient)?, spec, out, format)
+                },
+            ),
             revision::Subcommands::PreviousBranches => prepare_and_run(
                 "revision-previousbranches",
                 verbose,
diff --git a/src/plumbing/options.rs b/src/plumbing/options.rs
index 921e175a4b4..f6d9a4a98f5 100644
--- a/src/plumbing/options.rs
+++ b/src/plumbing/options.rs
@@ -222,6 +222,9 @@ pub mod revision {
     #[derive(Debug, clap::Subcommand)]
     #[clap(visible_alias = "rev", visible_alias = "r")]
     pub enum Subcommands {
+        /// List all commits reachable from the given rev-spec.
+        #[clap(visible_alias = "l")]
+        List { spec: std::ffi::OsString },
         /// Provide the revision specification like `@~1` to explain.
         #[clap(visible_alias = "e")]
         Explain { spec: std::ffi::OsString },