feat: no-repo index from-list to create an index with empty files f…

…rom the given list.

The list could be created with `find . -type f` for example.

gitoxide-core/src/repository/index/mod.rs

@@ -1,3 +1,4 @@
+use anyhow::bail;
 use std::{ffi::OsString, path::PathBuf};
 
 use gix::prelude::FindExt;
@@ -35,5 +36,48 @@ pub fn from_tree(
     Ok(())
 }
 
+pub fn from_list(entries_file: PathBuf, index_path: Option<PathBuf>, force: bool) -> anyhow::Result<()> {
+    use std::io::BufRead;
+    let object_hash = gix::hash::Kind::Sha1;
+
+    let mut index = gix::index::State::new(object_hash);
+    for path in std::io::BufReader::new(std::fs::File::open(&entries_file)?).lines() {
+        let path: PathBuf = path?.into();
+        if !path.is_relative() {
+            bail!("Input paths need to be relative, but {path:?} is not.")
+        }
+        let path = gix::path::into_bstr(path);
+        index.dangerously_push_entry(
+            gix::index::entry::Stat::default(),
+            gix::hash::ObjectId::empty_blob(object_hash),
+            gix::index::entry::Flags::empty(),
+            gix::index::entry::Mode::FILE,
+            gix::path::to_unix_separators_on_windows(path).as_ref(),
+        )
+    }
+    index.sort_entries();
+
+    let options = gix::index::write::Options::default();
+    match index_path {
+        Some(index_path) => {
+            if index_path.is_file() && !force {
+                anyhow::bail!(
+                    "File at \"{}\" already exists, to overwrite use the '-f' flag",
+                    index_path.display()
+                );
+            }
+            let mut index = gix::index::File::from_state(index, index_path);
+            index.write(options)?;
+        }
+        None => {
+            let index = gix::index::File::from_state(index, std::path::PathBuf::new());
+            let mut out = Vec::with_capacity(512 * 1024);
+            index.write_to(&mut out, options)?;
+        }
+    }
+
+    Ok(())
+}
+
 pub mod entries;
 pub use entries::function::entries;

src/plumbing/main.rs

@@ -293,14 +293,26 @@ pub fn main() -> Result<()> {
                 index_path,
                 cmd,
             }) => match cmd {
+                free::index::Subcommands::FromList {
+                    force,
+                    index_output_path,
+                    file,
+                } => prepare_and_run(
+                    "index-from-list",
+                    verbose,
+                    progress,
+                    progress_keep_open,
+                    None,
+                    move |_progress, _out, _err| core::repository::index::from_list(file, index_output_path, force),
+                ),
                 free::index::Subcommands::CheckoutExclusive {
                     directory,
                     empty_files,
                     repository,
                     keep_going,
                 } => prepare_and_run(
                     "index-checkout",
-                    verbose,
+                    auto_verbose,
                     progress,
                     progress_keep_open,
                     None,

src/plumbing/options/free.rs

@@ -53,6 +53,19 @@ pub mod index {
 
     #[derive(Debug, clap::Subcommand)]
     pub enum Subcommands {
+        /// Create an index from a list of empty files, one per line of the input.
+        FromList {
+            /// Overwrite the specified index file if it already exists.
+            #[clap(long, short = 'f')]
+            force: bool,
+            /// Path to the index file to be written.
+            /// If none is given it will be kept in memory only as a way to measure performance. One day we will probably write the index
+            /// back by default, but that requires us to write more of the index to work.
+            #[clap(long, short = 'i')]
+            index_output_path: Option<PathBuf>,
+            /// The file to read the index entries from, one path per line.
+            file: PathBuf,
+        },
         /// Validate constraints and assumptions of an index along with its integrity.
         Verify,
         /// Print information about the index structure