//! /// An empty array of a type usable with the `git::easy` API to help declaring no parents should be usedpub const NO_PARENT_IDS: [git_hash::ObjectId; 0] = []; /// The error returned by [`commit(…)`][crate::Repository::commit()].#[derive(Debug, thiserror::Error)]#[allow(missing_docs)]pub enum Error {    #[error("Committer identity is not configured")]    CommitterMissing,    #[error("Author identity is not conifgured")]    AuthorMissing,    #[error(transparent)]    ReferenceNameValidation(#[from] git_ref::name::Error),    #[error(transparent)]    WriteObject(#[from] crate::object::write::Error),    #[error(transparent)]    ReferenceEdit(#[from] crate::reference::edit::Error),} ///pub mod describe {    use std::borrow::Cow;     use git_hash::ObjectId;    use git_hashtable::HashMap;    use git_odb::Find;     use crate::{bstr::BStr, ext::ObjectIdExt, Repository};     /// The result of [try_resolve()][Platform::try_resolve()].    pub struct Resolution<'repo> {        /// The outcome of the describe operation.        pub outcome: git_revision::describe::Outcome<'static>,        /// The id to describe.        pub id: crate::Id<'repo>,    }     impl<'repo> Resolution<'repo> {        /// Turn this instance into something displayable        pub fn format(self) -> Result<git_revision::describe::Format<'static>, Error> {            let prefix = self.id.shorten()?;            Ok(self.outcome.into_format(prefix.hex_len()))        }    }     /// The error returned by [try_format()][Platform::try_format()].    #[derive(Debug, thiserror::Error)]    #[allow(missing_docs)]    pub enum Error {        #[error(transparent)]        Describe(#[from] git_revision::describe::Error<git_odb::store::find::Error>),        #[error("Could not produce an unambiguous shortened id for formatting.")]        ShortId(#[from] crate::id::shorten::Error),        #[error(transparent)]        RefIter(#[from] crate::reference::iter::Error),        #[error(transparent)]        RefIterInit(#[from] crate::reference::iter::init::Error),    }     /// A selector to choose what kind of references should contribute to names.    #[derive(Debug, Clone, Copy, PartialOrd, PartialEq, Ord, Eq, Hash)]    pub enum SelectRef {        /// Only use annotated tags for names.        AnnotatedTags,        /// Use all tags for names, annotated or plain reference.        AllTags,        /// Use all references, including local branch names.        AllRefs,    }     impl SelectRef {        fn names(&self, repo: &Repository) -> Result<HashMap<ObjectId, Cow<'static, BStr>>, Error> {            let platform = repo.references()?;             Ok(match self {                SelectRef::AllTags | SelectRef::AllRefs => {                    let mut refs: Vec<_> = match self {                        SelectRef::AllRefs => platform.all()?,                        SelectRef::AllTags => platform.tags()?,                        _ => unreachable!(),                    }                    .filter_map(Result::ok)                    .filter_map(|mut r: crate::Reference<'_>| {                        let target_id = r.target().try_id().map(ToOwned::to_owned);                        let peeled_id = r.peel_to_id_in_place().ok()?;                        let (prio, tag_time) = match target_id {                            Some(target_id) if peeled_id != *target_id => {                                let tag = repo.find_object(target_id).ok()?.try_into_tag().ok()?;                                (1, tag.tagger().ok()??.time.seconds_since_unix_epoch)                            }                            _ => (0, 0),                        };                        (                            peeled_id.inner,                            prio,                            tag_time,                            Cow::from(r.inner.name.shorten().to_owned()),                        )                            .into()                    })                    .collect();                    // By priority, then by time ascending, then lexicographically.                    // More recent entries overwrite older ones due to collection into hashmap.                    refs.sort_by(                        |(_a_peeled_id, a_prio, a_time, a_name), (_b_peeled_id, b_prio, b_time, b_name)| {                            a_prio                                .cmp(b_prio)                                .then_with(|| a_time.cmp(b_time))                                .then_with(|| b_name.cmp(a_name))                        },                    );                    refs.into_iter().map(|(a, _, _, b)| (a, b)).collect()                }                SelectRef::AnnotatedTags => {                    let mut peeled_commits_and_tag_date: Vec<_> = platform                        .tags()?                        .filter_map(Result::ok)                        .filter_map(|r: crate::Reference<'_>| {                            // TODO: we assume direct refs for tags, which is the common case, but it doesn't have to be                            //       so rather follow symrefs till the first object and then peel tags after the first object was found.                            let tag = r.try_id()?.object().ok()?.try_into_tag().ok()?;                            let tag_time = tag                                .tagger()                                .ok()                                .and_then(|s| s.map(|s| s.time.seconds_since_unix_epoch))                                .unwrap_or(0);                            let commit_id = tag.target_id().ok()?.object().ok()?.try_into_commit().ok()?.id;                            Some((commit_id, tag_time, Cow::<BStr>::from(r.name().shorten().to_owned())))                        })                        .collect();                    // Sort by time ascending, then lexicographically.                    // More recent entries overwrite older ones due to collection into hashmap.                    peeled_commits_and_tag_date.sort_by(|(_a_id, a_time, a_name), (_b_id, b_time, b_name)| {                        a_time.cmp(b_time).then_with(|| b_name.cmp(a_name))                    });                    peeled_commits_and_tag_date                        .into_iter()                        .map(|(a, _, c)| (a, c))                        .collect()                }            })        }    }     impl Default for SelectRef {        fn default() -> Self {            SelectRef::AnnotatedTags        }    }     /// A support type to allow configuring a `git describe` operation    pub struct Platform<'repo> {        pub(crate) id: git_hash::ObjectId,        pub(crate) repo: &'repo crate::Repository,        pub(crate) select: SelectRef,        pub(crate) first_parent: bool,        pub(crate) id_as_fallback: bool,        pub(crate) max_candidates: usize,    }     impl<'repo> Platform<'repo> {        /// Configure which names to `select` from which describe can chose.        pub fn names(mut self, select: SelectRef) -> Self {            self.select = select;            self        }         /// If true, shorten the graph traversal time by just traversing the first parent of merge commits.        pub fn traverse_first_parent(mut self, first_parent: bool) -> Self {            self.first_parent = first_parent;            self        }         /// Only consider the given amount of candidates, instead of the default of 10.        pub fn max_candidates(mut self, candidates: usize) -> Self {            self.max_candidates = candidates;            self        }         /// If true, even if no candidate is available a format will always be produced.        pub fn id_as_fallback(mut self, use_fallback: bool) -> Self {            self.id_as_fallback = use_fallback;            self        }         /// Try to find a name for the configured commit id using all prior configuration, returning `Some(describe::Format)`        /// if one was found.        ///        /// Note that there will always be `Some(format)`        pub fn try_format(&self) -> Result<Option<git_revision::describe::Format<'static>>, Error> {            self.try_resolve()?.map(|r| r.format()).transpose()        }         /// Try to find a name for the configured commit id using all prior configuration, returning `Some(Outcome)`        /// if one was found.        ///        /// The outcome provides additional information, but leaves the caller with the burden        ///        /// # Performance        ///        /// It is greatly recommended to [assure an object cache is set][crate::Repository::object_cache_size_if_unset()]        /// to save ~40% of time.        pub fn try_resolve(&self) -> Result<Option<Resolution<'repo>>, Error> {            // TODO: dirty suffix with respective dirty-detection            let outcome = git_revision::describe(                &self.id,                |id, buf| {                    Ok(self                        .repo                        .objects                        .try_find(id, buf)?                        .and_then(|d| d.try_into_commit_iter()))                },                git_revision::describe::Options {                    name_by_oid: self.select.names(self.repo)?,                    fallback_to_oid: self.id_as_fallback,                    first_parent: self.first_parent,                    max_candidates: self.max_candidates,                },            )?;             Ok(outcome.map(|outcome| crate::commit::describe::Resolution {                outcome,                id: self.id.attach(self.repo),            }))        }         /// Like [`try_format()`][Platform::try_format()], but turns `id_as_fallback()` on to always produce a format.        pub fn format(&mut self) -> Result<git_revision::describe::Format<'static>, Error> {            self.id_as_fallback = true;            Ok(self.try_format()?.expect("BUG: fallback must always produce a format"))        }    }}