feat: allow disabling the blob-diff capability

This also removes all diff capabilities.

Author: Byron

gix/Cargo.toml

@@ -58,7 +58,7 @@ default = ["max-performance-safe", "comfort", "extras"]
 #! Bundles are for convenience only and bear no further meaning beyond the cargo manifest file.
 
 ## Various additional features and capabilities that are not necessarily part of what most users would need.
-extras = ["worktree-stream", "worktree-archive"]
+extras = ["worktree-stream", "worktree-archive", "blob-diff"]
 
 ## Various progress-related features that improve the look of progress message units.
 comfort = ["gix-features/progress-unit-bytes", "gix-features/progress-unit-human-numbers"]
@@ -68,6 +68,10 @@ comfort = ["gix-features/progress-unit-bytes", "gix-features/progress-unit-human
 #! A component is a distinct feature which may be comprised of one or more methods around a particular topic.
 #! Providers of libraries should only activate
 
+## Make it possible to diff blobs line by line. Note that this feature is integral for implementing tree-diffs as well due to the handling of rename-tracking,
+## which relies on line-by-line diffs in some cases.
+blob-diff = ["gix-diff/blob"]
+
 ## Make it possible to turn a tree into a stream of bytes, which can be decoded to entries and turned into various other formats.
 worktree-stream = ["gix-worktree-stream"]
 
@@ -189,7 +193,7 @@ gix-negotiate = { version = "^0.6.0", path = "../gix-negotiate" }
 gix-path = { version = "^0.9.0", path = "../gix-path" }
 gix-url = { version = "^0.22.0", path = "../gix-url" }
 gix-traverse = { version = "^0.31.0", path = "../gix-traverse" }
-gix-diff = { version = "^0.34.0", path = "../gix-diff" }
+gix-diff = { version = "^0.34.0", path = "../gix-diff", default-features = false }
 gix-mailmap = { version = "^0.17.0", path = "../gix-mailmap" }
 gix-features = { version = "^0.33.0", path = "../gix-features", features = ["progress", "once_cell"] }
 gix-trace = { version = "^0.1.3", path = "../gix-trace" }

gix/src/config/cache/access.rs

@@ -9,7 +9,7 @@ use crate::{
     config,
     config::{
         boolean,
-        cache::util::{ApplyLeniency, ApplyLeniencyDefault, ApplyLeniencyDefaultValue},
+        cache::util::{ApplyLeniency, ApplyLeniencyDefaultValue},
         checkout_options,
         tree::{gitoxide, Checkout, Core, Key},
         Cache,
@@ -21,7 +21,9 @@ use crate::{
 
 /// Access
 impl Cache {
+    #[cfg(feature = "blob-diff")]
     pub(crate) fn diff_algorithm(&self) -> Result<gix_diff::blob::Algorithm, config::diff::algorithm::Error> {
+        use crate::config::cache::util::ApplyLeniencyDefault;
         use crate::config::diff::algorithm::Error;
         self.diff_algorithm
             .get_or_try_init(|| {
@@ -82,6 +84,7 @@ impl Cache {
             })
     }
 
+    #[cfg(feature = "blob-diff")]
     pub(crate) fn diff_renames(
         &self,
     ) -> Result<Option<crate::object::tree::diff::Rewrites>, crate::object::tree::diff::rewrites::Error> {

gix/src/config/cache/init.rs

@@ -174,9 +174,11 @@ impl Cache {
             user_agent: Default::default(),
             personas: Default::default(),
             url_rewrite: Default::default(),
+            #[cfg(feature = "blob-diff")]
             diff_renames: Default::default(),
             #[cfg(any(feature = "blocking-network-client", feature = "async-network-client"))]
             url_scheme: Default::default(),
+            #[cfg(feature = "blob-diff")]
             diff_algorithm: Default::default(),
         })
     }
@@ -222,8 +224,11 @@ impl Cache {
         self.user_agent = Default::default();
         self.personas = Default::default();
         self.url_rewrite = Default::default();
-        self.diff_renames = Default::default();
-        self.diff_algorithm = Default::default();
+        #[cfg(feature = "blob-diff")]
+        {
+            self.diff_renames = Default::default();
+            self.diff_algorithm = Default::default();
+        }
         (
             self.static_pack_cache_limit_bytes,
             self.pack_cache_bytes,

gix/src/config/mod.rs

@@ -495,11 +495,13 @@ pub(crate) struct Cache {
     /// A lazily loaded rewrite list for remote urls
     pub(crate) url_rewrite: OnceCell<crate::remote::url::Rewrite>,
     /// The lazy-loaded rename information for diffs.
+    #[cfg(feature = "blob-diff")]
     pub(crate) diff_renames: OnceCell<Option<crate::object::tree::diff::Rewrites>>,
     /// A lazily loaded mapping to know which url schemes to allow
     #[cfg(any(feature = "blocking-network-client", feature = "async-network-client"))]
     pub(crate) url_scheme: OnceCell<crate::remote::url::SchemePermission>,
     /// The algorithm to use when diffing blobs
+    #[cfg(feature = "blob-diff")]
     pub(crate) diff_algorithm: OnceCell<gix_diff::blob::Algorithm>,
     /// The amount of bytes to use for a memory backed delta pack cache. If `Some(0)`, no cache is used, if `None`
     /// a standard cache is used which costs near to nothing and always pays for itself.

gix/src/config/tree/mod.rs

@@ -31,6 +31,7 @@ pub(crate) mod root {
         /// The `credential` section.
         pub const CREDENTIAL: sections::Credential = sections::Credential;
         /// The `diff` section.
+        #[cfg(feature = "blob-diff")]
         pub const DIFF: sections::Diff = sections::Diff;
         /// The `extensions` section.
         pub const EXTENSIONS: sections::Extensions = sections::Extensions;
@@ -69,6 +70,7 @@ pub(crate) mod root {
                 &Self::COMMITTER,
                 &Self::CORE,
                 &Self::CREDENTIAL,
+                #[cfg(feature = "blob-diff")]
                 &Self::DIFF,
                 &Self::EXTENSIONS,
                 &Self::FETCH,
@@ -90,10 +92,12 @@ pub(crate) mod root {
 
 mod sections;
 pub use sections::{
-    branch, checkout, core, credential, diff, extensions, fetch, gitoxide, http, index, protocol, remote, ssh, Author,
-    Branch, Checkout, Clone, Committer, Core, Credential, Diff, Extensions, Fetch, Gitoxide, Http, Index, Init, Pack,
+    branch, checkout, core, credential, extensions, fetch, gitoxide, http, index, protocol, remote, ssh, Author,
+    Branch, Checkout, Clone, Committer, Core, Credential, Extensions, Fetch, Gitoxide, Http, Index, Init, Pack,
     Protocol, Remote, Safe, Ssh, Url, User,
 };
+#[cfg(feature = "blob-diff")]
+pub use sections::{diff, Diff};
 
 /// Generic value implementations for static instantiation.
 pub mod keys;

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

@@ -37,7 +37,9 @@ pub mod credential;
 
 /// The `diff` top-level section.
 #[derive(Copy, Clone, Default)]
+#[cfg(feature = "blob-diff")]
 pub struct Diff;
+#[cfg(feature = "blob-diff")]
 pub mod diff;
 
 /// The `extension` top-level section.

gix/src/object/blob.rs

@@ -1,4 +1,5 @@
 ///
+#[cfg(feature = "blob-diff")]
 pub mod diff {
     use std::ops::Range;
 

gix/src/object/tree/mod.rs

@@ -168,6 +168,7 @@ impl<'repo> Tree<'repo> {
 }
 
 ///
+#[cfg(feature = "blob-diff")]
 pub mod diff;
 
 ///

gix/tests/config/tree.rs

@@ -204,6 +204,7 @@ mod fetch {
     }
 }
 
+#[cfg(feature = "blob-diff")]
 mod diff {
     use gix::{
         config::tree::{Diff, Key},

gix/tests/object/tree/mod.rs

@@ -1,5 +1,6 @@
 use crate::util::{named_repo, named_subrepo_opts};
 
+#[cfg(feature = "blob-diff")]
 mod diff;
 
 #[test]