feat!: respect the core.commitGraph option.

Previously, we would always use the commitgraph when available, but now we only do so
if the `core.commitGraph` option is set.

gix/src/config/cache/access.rs

@@ -4,6 +4,7 @@ use std::{borrow::Cow, path::PathBuf, time::Duration};
 use gix_attributes::Source;
 use gix_lock::acquire::Fail;
 
+use crate::config::cache::util::ApplyLeniencyDefaultValue;
 use crate::{
     bstr::BStr,
     config,
@@ -69,6 +70,18 @@ impl Cache {
             .get_or_try_init(|| remote::url::SchemePermission::from_config(&self.resolved, self.filter_config_section))
     }
 
+    pub(crate) fn may_use_commit_graph(&self) -> Result<bool, config::boolean::Error> {
+        const DEFAULT: bool = true;
+        self.resolved
+            .boolean_by_key("core.commitGraph")
+            .map(|res| {
+                Core::COMMIT_GRAPH
+                    .enrich_error(res)
+                    .with_lenient_default_value(self.lenient_config, DEFAULT)
+            })
+            .unwrap_or(Ok(DEFAULT))
+    }
+
     pub(crate) fn diff_renames(
         &self,
     ) -> Result<Option<crate::object::tree::diff::Rewrites>, crate::object::tree::diff::rewrites::Error> {

gix/src/config/cache/util.rs

@@ -124,6 +124,10 @@ pub trait ApplyLeniencyDefault {
     fn with_lenient_default(self, is_lenient: bool) -> Self;
 }
 
+pub trait ApplyLeniencyDefaultValue<T> {
+    fn with_lenient_default_value(self, is_lenient: bool, default: T) -> Self;
+}
+
 impl<T, E> ApplyLeniency for Result<Option<T>, E> {
     fn with_leniency(self, is_lenient: bool) -> Self {
         match self {
@@ -146,3 +150,13 @@ where
         }
     }
 }
+
+impl<T, E> ApplyLeniencyDefaultValue<T> for Result<T, E> {
+    fn with_lenient_default_value(self, is_lenient: bool, default: T) -> Self {
+        match self {
+            Ok(v) => Ok(v),
+            Err(_) if is_lenient => Ok(default),
+            Err(err) => Err(err),
+        }
+    }
+}

gix/src/config/tree/sections/core.rs

@@ -66,6 +66,8 @@ impl Core {
     /// The `core.useReplaceRefs` key.
     pub const USE_REPLACE_REFS: keys::Boolean = keys::Boolean::new_boolean("useReplaceRefs", &config::Tree::CORE)
         .with_environment_override("GIT_NO_REPLACE_OBJECTS");
+    /// The `core.commitGraph` key.
+    pub const COMMIT_GRAPH: keys::Boolean = keys::Boolean::new_boolean("commitGraph", &config::Tree::CORE);
 }
 
 impl Section for Core {
@@ -96,6 +98,7 @@ impl Section for Core {
             &Self::ATTRIBUTES_FILE,
             &Self::SSH_COMMAND,
             &Self::USE_REPLACE_REFS,
+            &Self::COMMIT_GRAPH,
         ]
     }
 }

gix/src/repository/graph.rs

@@ -7,6 +7,9 @@ impl crate::Repository {
     /// Note that the commitgraph will be used if it is present and readable, but it won't be an error if it is corrupted. In that case,
     /// it will just not be used.
     ///
+    /// Note that a commitgraph is only allowed to be used if `core.commitGraph` is true (the default), and that configuration errors are
+    /// ignored as well.
+    ///
     /// ### Performance
     ///
     /// Note that the [Graph][gix_revision::Graph] can be sensitive to various object database settings that may affect the performance
@@ -18,7 +21,11 @@ impl crate::Repository {
                     .try_find(id, buf)
                     .map(|r| r.and_then(|d| d.try_into_commit_iter()))
             },
-            gix_commitgraph::at(self.objects.store_ref().path().join("info")).ok(),
+            self.config
+                .may_use_commit_graph()
+                .unwrap_or(true)
+                .then(|| gix_commitgraph::at(self.objects.store_ref().path().join("info")).ok())
+                .flatten(),
         )
     }
 

gix/src/revision/walk.rs

@@ -12,6 +12,8 @@ pub enum Error {
     AncestorIter(#[from] gix_traverse::commit::ancestors::Error),
     #[error(transparent)]
     ShallowCommits(#[from] crate::shallow::open::Error),
+    #[error(transparent)]
+    ConfigBoolean(#[from] crate::config::boolean::Error),
 }
 
 /// Information about a commit that we obtained naturally as part of the iteration.
@@ -92,7 +94,7 @@ pub struct Platform<'repo> {
     pub(crate) tips: Vec<ObjectId>,
     pub(crate) sorting: gix_traverse::commit::Sorting,
     pub(crate) parents: gix_traverse::commit::Parents,
-    pub(crate) use_commit_graph: bool,
+    pub(crate) use_commit_graph: Option<bool>,
     pub(crate) commit_graph: Option<gix_commitgraph::Graph>,
 }
 
@@ -103,7 +105,7 @@ impl<'repo> Platform<'repo> {
             tips: tips.into_iter().map(Into::into).collect(),
             sorting: Default::default(),
             parents: Default::default(),
-            use_commit_graph: true,
+            use_commit_graph: None,
             commit_graph: None,
         }
     }
@@ -123,12 +125,12 @@ impl<'repo> Platform<'repo> {
         self
     }
 
-    /// Allow using the commitgraph, if present, if `toggle` is `true`, or disallow it with `false`.
+    /// Allow using the commitgraph, if present, if `toggle` is `true`, or disallow it with `false`. Set it to `None` to leave
+    /// control over this to the configuration of `core.commitGraph` (the default).
     ///
-    /// Note that the commitgraph will be used by default, and that errors just lead to falling back to the object database,
-    /// it's treated as a cache.
-    pub fn use_commit_graph(mut self, toggle: bool) -> Self {
-        self.use_commit_graph = toggle;
+    /// Errors when loading the graph lead to falling back to the object database, it's treated as optional cache.
+    pub fn use_commit_graph(mut self, toggle: impl Into<Option<bool>>) -> Self {
+        self.use_commit_graph = toggle.into();
         self
     }
 
@@ -201,7 +203,12 @@ impl<'repo> Platform<'repo> {
                 )
                 .sorting(sorting)?
                 .parents(parents)
-                .commit_graph(commit_graph.or(use_commit_graph.then(|| self.repo.commit_graph().ok()).flatten())),
+                .commit_graph(
+                    commit_graph.or(use_commit_graph
+                        .map_or_else(|| self.repo.config.may_use_commit_graph(), Ok)?
+                        .then(|| self.repo.commit_graph().ok())
+                        .flatten()),
+                ),
             ),
         })
     }