Add internal-tools git-to-sh to serialize a git repo partially to a…

… shell script.

The shell-script will reproduce the repository, as long as the history is linear.

tests/it/Cargo.toml

@@ -15,5 +15,5 @@ path = "src/main.rs"
 clap = { version = "4.5.16", features = ["derive"] }
 anyhow = "1.0.86"
 
-gix = { version = "0.64.0", path = "../../gix", default-features = false, features = ["attributes"] }
+gix = { version = "0.64.0", path = "../../gix", default-features = false, features = ["attributes", "revision"] }
 

tests/it/src/args.rs

@@ -31,6 +31,37 @@ pub enum Subcommands {
         #[clap(value_parser = AsPathSpec)]
         patterns: Vec<gix::pathspec::Pattern>,
     },
+    /// Serialize a git repository as linear history while degenerating content into a shell script that reproduces it.
+    #[clap(visible_alias = "gts")]
+    GitToSh {
+        /// The amount of commits to copy from `committish`.
+        ///
+        /// If 0, all traversable commits will be copied.
+        #[clap(long, short = 'c', default_value_t = 0)]
+        count: usize,
+        /// Do not use `copy-royal` to degenerate information of blobs, but take blobs verbatim.
+        ///
+        /// Note that this should only be done if the source repository is purely for testing
+        /// or was created by yourself.
+        #[clap(long)]
+        verbatim: bool,
+        /// The directory into which the blobs and tree declarations will be written.
+        #[clap(long, short = 'o', default_value = ".")]
+        output_dir: PathBuf,
+        /// The path to the git repository to serialize.
+        repo_dir: PathBuf,
+        /// The name of the directory within `output_dir` for storing blobs and trees.
+        name: String,
+        /// A revspec of the commit to start the iteration from, like `@`.
+        ///
+        /// Note that the history will be serialized, and multiple parents aren't allowed.
+        committish: String,
+        /// The pathspecs to determine which paths to copy from each commit's tree.
+        ///
+        /// None will copy everything.
+        #[clap(value_parser = AsPathSpec)]
+        patterns: Vec<gix::pathspec::Pattern>,
+    },
 }
 
 #[derive(Clone)]

tests/it/src/commands/copy_royal.rs

@@ -1,111 +1,114 @@
-use anyhow::Context;
-use gix::fs::Stack;
-use gix::pathspec::Pattern;
-use std::path::{Path, PathBuf};
+pub(super) mod function {
+    use anyhow::Context;
+    use gix::fs::Stack;
+    use gix::pathspec::Pattern;
+    use std::path::{Path, PathBuf};
 
-pub fn doit(
-    dry_run: bool,
-    worktree_dir: &Path,
-    destination_dir: PathBuf,
-    patterns: Vec<Pattern>,
-) -> anyhow::Result<()> {
-    let prefix = if dry_run { "WOULD" } else { "Will" };
-    let repo = gix::open(worktree_dir)?;
-    let index = repo.index()?;
-    let mut specs = repo.pathspec(
-        true,
-        // TODO: ideally this could accept patterns already.
-        patterns.into_iter().map(|p| p.to_bstring()),
-        true,
-        &index,
-        gix::worktree::stack::state::attributes::Source::WorktreeThenIdMapping,
-    )?;
-    let mut create_dir = CreateDir { dry_run };
-    let mut stack = gix::fs::Stack::new(destination_dir);
-    for (rela_path, _entry) in specs
-        .index_entries_with_paths(&index)
-        .context("Didn't find a single entry to copy")?
-    {
-        let rela_path = gix::path::from_bstr(rela_path);
-        let src = worktree_dir.join(&rela_path);
-        stack.make_relative_path_current(&rela_path, &mut create_dir)?;
-        let dst = stack.current();
+    pub fn copy_royal(
+        dry_run: bool,
+        worktree_dir: &Path,
+        destination_dir: PathBuf,
+        patterns: Vec<Pattern>,
+    ) -> anyhow::Result<()> {
+        let prefix = if dry_run { "WOULD" } else { "Will" };
+        let repo = gix::open(worktree_dir)?;
+        let index = repo.index()?;
+        let mut specs = repo.pathspec(
+            true,
+            // TODO: ideally this could accept patterns already.
+            patterns.into_iter().map(|p| p.to_bstring()),
+            true,
+            &index,
+            gix::worktree::stack::state::attributes::Source::WorktreeThenIdMapping,
+        )?;
+        let mut create_dir = CreateDir { dry_run };
+        let mut stack = gix::fs::Stack::new(destination_dir);
+        for (rela_path, _entry) in specs
+            .index_entries_with_paths(&index)
+            .context("Didn't find a single entry to copy")?
+        {
+            let rela_path = gix::path::from_bstr(rela_path);
+            let src = worktree_dir.join(&rela_path);
+            stack.make_relative_path_current(&rela_path, &mut create_dir)?;
+            let dst = stack.current();
 
-        eprintln!(
-            "{prefix} copy '{src}' to '{dst}'",
-            src = src.display(),
-            dst = dst.display()
-        );
-        if !dry_run {
-            let content = std::fs::read_to_string(&src).with_context(|| {
-                format!(
-                    "Need UTF-8 decodable content in '{src}' - skip binaries with pathspec",
-                    src = src.display()
-                )
-            })?;
-            std::fs::write(dst, remapped(content))?
+            eprintln!(
+                "{prefix} copy '{src}' to '{dst}'",
+                src = src.display(),
+                dst = dst.display()
+            );
+            if !dry_run {
+                let content = std::fs::read_to_string(&src).with_context(|| {
+                    format!(
+                        "Need UTF-8 decodable content in '{src}' - skip binaries with pathspec",
+                        src = src.display()
+                    )
+                })?;
+                std::fs::write(dst, remapped(&content))?
+            }
         }
+        Ok(())
     }
-    Ok(())
-}
 
-fn remapped(i: String) -> String {
-    i.chars()
-        .filter_map(|c| {
-            Some(if c.is_alphabetic() {
-                if c.is_uppercase() {
-                    match (c as u32) % 10 {
-                        0 => 'A',
-                        1 => 'E',
-                        2 => 'I',
-                        3 => 'O',
-                        4 => 'U',
-                        5 => 'X',
-                        6 => 'R',
-                        7 => 'S',
-                        8 => 'T',
-                        9 => 'Y',
-                        _ => unreachable!(),
+    pub fn remapped(i: &str) -> String {
+        i.chars()
+            .filter_map(|c| {
+                Some(if c.is_alphabetic() {
+                    if c.is_uppercase() {
+                        match (c as u32) % 10 {
+                            0 => 'A',
+                            1 => 'E',
+                            2 => 'I',
+                            3 => 'O',
+                            4 => 'U',
+                            5 => 'X',
+                            6 => 'R',
+                            7 => 'S',
+                            8 => 'T',
+                            9 => 'Y',
+                            _ => unreachable!(),
+                        }
+                    } else {
+                        match (c as u32) % 10 {
+                            0 => 'a',
+                            1 => 'e',
+                            2 => 'i',
+                            3 => 'o',
+                            4 => 'u',
+                            5 => 'x',
+                            6 => 'r',
+                            7 => 's',
+                            8 => 't',
+                            9 => 'y',
+                            _ => unreachable!(),
+                        }
                     }
+                } else if c.is_whitespace() || c.is_ascii_punctuation() || c.is_ascii_digit() {
+                    c
                 } else {
-                    match (c as u32) % 10 {
-                        0 => 'a',
-                        1 => 'e',
-                        2 => 'i',
-                        3 => 'o',
-                        4 => 'u',
-                        5 => 'x',
-                        6 => 'r',
-                        7 => 's',
-                        8 => 't',
-                        9 => 'y',
-                        _ => unreachable!(),
-                    }
-                }
-            } else if c.is_whitespace() || c.is_ascii_punctuation() || c.is_ascii_digit() {
-                c
-            } else {
-                return None;
+                    return None;
+                })
             })
-        })
-        .collect()
-}
+            .collect()
+    }
 
-struct CreateDir {
-    dry_run: bool,
-}
+    struct CreateDir {
+        dry_run: bool,
+    }
 
-impl gix::fs::stack::Delegate for CreateDir {
-    fn push_directory(&mut self, stack: &Stack) -> std::io::Result<()> {
-        if !self.dry_run && !stack.current().is_dir() {
-            std::fs::create_dir(stack.current())?;
+    impl gix::fs::stack::Delegate for CreateDir {
+        fn push_directory(&mut self, stack: &Stack) -> std::io::Result<()> {
+            if !self.dry_run && !stack.current().is_dir() {
+                std::fs::create_dir(stack.current())?;
+            }
+            Ok(())
         }
-        Ok(())
-    }
 
-    fn push(&mut self, _is_last_component: bool, _stack: &Stack) -> std::io::Result<()> {
-        Ok(())
-    }
+        fn push(&mut self, _is_last_component: bool, _stack: &Stack) -> std::io::Result<()> {
+            Ok(())
+        }
 
-    fn pop_directory(&mut self) {}
+        fn pop_directory(&mut self) {}
+    }
 }
+pub use function::remapped;

tests/it/src/commands/git_to_sh.rs

@@ -0,0 +1,137 @@
+pub struct Options {
+    pub patterns: Vec<gix::pathspec::Pattern>,
+    pub verbatim: bool,
+    pub max_count: usize,
+}
+
+pub(super) mod function {
+    use anyhow::{bail, Context};
+    use gix::object::tree::EntryKind;
+    use gix::objs::FindExt;
+    use std::borrow::Cow;
+    use std::path::Path;
+
+    use super::Options;
+
+    pub fn git_to_sh(
+        output_dir: &Path,
+        repo_dir: &Path,
+        name: &str,
+        committish: &str,
+        mut out: impl std::io::Write,
+        Options {
+            patterns,
+            verbatim,
+            max_count,
+        }: Options,
+    ) -> anyhow::Result<()> {
+        let repo = gix::open(repo_dir)?;
+        let commit = repo.rev_parse_single(committish)?.object()?.try_into_commit()?;
+
+        let assets = output_dir.join(name);
+        std::fs::create_dir_all(&assets)?;
+
+        let mut commits = Vec::new();
+        let mut tree_buf = Vec::new();
+        let mut current = 0;
+        for entry in commit.id().ancestors().first_parent_only().all()? {
+            let entry = entry?;
+
+            let commit = entry.id().object()?.into_commit();
+            commits.push((commit.id, commit.message_raw_sloppy().to_owned()));
+            let index = repo.index_from_tree(&commit.tree_id()?)?;
+
+            tree_buf.clear();
+            write_tree_as_update_index_format(&repo, &index, &mut tree_buf, &assets, verbatim, patterns.clone())?;
+
+            let tree_file = assets.join(format!("{}.tree", commit.id));
+            std::fs::write(tree_file, &tree_buf)?;
+            current += 1;
+
+            if current >= max_count {
+                break;
+            }
+        }
+
+        writeln!(
+            &mut out,
+            "# The following is to be executed in the receiving git repository"
+        )?;
+        writeln!(&mut out, "ROOT=to-be-specified-by-user")?;
+        writeln!(&mut out, "index=.git/index")?;
+        writeln!(&mut out, "git hash-object -w -t blob -- $ROOT/{name}/*.blob")?;
+        for (commit_id, commit_msg) in commits.iter().rev() {
+            writeln!(&mut out, "rm \"$index\"")?;
+            writeln!(
+                &mut out,
+                "git update-index --index-info < \"$ROOT/{name}/{commit_id}.tree\""
+            )?;
+            let commit_msg_file = assets.join(format!("{commit_id}.msg"));
+            std::fs::write(commit_msg_file, commit_msg)?;
+            writeln!(&mut out, "git commit --allow-empty -F \"$ROOT/{name}/{commit_id}.msg\"")?;
+        }
+
+        Ok(())
+    }
+
+    fn write_tree_as_update_index_format(
+        repo: &gix::Repository,
+        index: &gix::index::State,
+        out: &mut dyn std::io::Write,
+        output_dir: &Path,
+        verbatim: bool,
+        patterns: Vec<gix::pathspec::Pattern>,
+    ) -> anyhow::Result<()> {
+        let mut blob_buf = Vec::new();
+        let mut specs = repo.pathspec(
+            true,
+            // TODO: ideally this could accept patterns already.
+            patterns.clone().into_iter().map(|p| p.to_bstring()),
+            true,
+            index,
+            gix::worktree::stack::state::attributes::Source::IdMapping,
+        )?;
+
+        for (rela_path, entry) in specs.index_entries_with_paths(index).into_iter().flatten() {
+            if rela_path.contains(&b'\n') {
+                bail!("Entry at '{rela_path}' contained a newline, which currently can't be encoded. Preferred newlines over NULL separation.")
+            }
+
+            let (blob_id, blob_data) = match entry.mode.to_tree_entry_mode() {
+                None => {
+                    bail!("Couldn't interpret mode of tree entry at '{rela_path}'")
+                }
+                Some(mode) => match mode.kind() {
+                    EntryKind::Tree => {
+                        unreachable!("Can't have trees in indices")
+                    }
+                    EntryKind::Blob | EntryKind::BlobExecutable => {
+                        let obj = repo.objects.find(&entry.id, &mut blob_buf)?;
+                        if verbatim {
+                            (entry.id, Cow::Borrowed(&blob_buf))
+                        } else {
+                            let data = std::str::from_utf8(obj.data).with_context(|| {
+                                format!("Entry at '{rela_path}' was not valid UTF8 and can't be remapped")
+                            })?;
+                            let mapped = crate::commands::copy_royal::remapped(data);
+                            (
+                                gix::objs::compute_hash(repo.object_hash(), gix::object::Kind::Blob, mapped.as_bytes()),
+                                Cow::Owned(mapped.into()),
+                            )
+                        }
+                    }
+                    EntryKind::Link => {
+                        repo.objects.find(&entry.id, &mut blob_buf)?;
+                        (entry.id, Cow::Borrowed(&blob_buf))
+                    }
+                    EntryKind::Commit => continue,
+                },
+            };
+            let blob_path = output_dir.join(format!("{blob_id}.blob"));
+            std::fs::write(blob_path, blob_data.as_ref())?;
+
+            writeln!(out, "{mode:06o} {blob_id}\t{rela_path}", mode = entry.mode)?;
+        }
+        Ok(())
+    }
+}