Make url optional via a new "cred" feature gate for credential helpers

Add an enabled-by-default feature flag for credential helpers, which are
the only uses of the `url` crate. This reduces a
`default-features = false` build of git2 from 54 dependencies to 17, for
a configuration that many tools (e.g. anything that only cares about
local repositories) can happily use.

In addition to enabling it by default, make the "https" and "ssh"
features depend on "cred".

Author: joshtriplett

Cargo.toml

@@ -16,7 +16,7 @@ categories = ["api-bindings"]
 edition = "2018"
 
 [dependencies]
-url = "2.5.4"
+url = { version = "2.5.4", optional = true }
 bitflags = "2.1.0"
 libc = "0.2"
 log = "0.4.8"
@@ -30,12 +30,15 @@ openssl-probe = { version = "0.1", optional = true }
 clap = { version = "4.4.13", features = ["derive"] }
 time = { version = "0.3.37", features = ["formatting"] }
 tempfile = "3.1.0"
+url = "2.5.4"
 
 [features]
 unstable = []
-default = ["ssh", "https"]
-ssh = ["libgit2-sys/ssh"]
-https = ["libgit2-sys/https", "openssl-sys", "openssl-probe"]
+default = ["ssh", "https", "cred"]
+ssh = ["libgit2-sys/ssh", "cred"]
+https = ["libgit2-sys/https", "openssl-sys", "openssl-probe", "cred"]
+# Include support for credentials, which pulls in the `url` crate and all its dependencies
+cred = ["dep:url"]
 vendored-libgit2 = ["libgit2-sys/vendored"]
 vendored-openssl = ["openssl-sys/vendored", "libgit2-sys/vendored-openssl"]
 zlib-ng-compat = ["libgit2-sys/zlib-ng-compat"]

src/cred.rs

@@ -1,20 +1,22 @@
+#[cfg(feature = "cred")]
 use log::{debug, trace};
 use std::ffi::CString;
-use std::io::Write;
 use std::mem;
 use std::path::Path;
-use std::process::{Command, Stdio};
 use std::ptr;
 
 use crate::util::Binding;
-use crate::{raw, Config, Error, IntoCString};
+#[cfg(feature = "cred")]
+use crate::Config;
+use crate::{raw, Error, IntoCString};
 
 /// A structure to represent git credentials in libgit2.
 pub struct Cred {
     raw: *mut raw::git_cred,
 }
 
 /// Management of the gitcredentials(7) interface.
+#[cfg(feature = "cred")]
 pub struct CredentialHelper {
     /// A public field representing the currently discovered username from
     /// configuration.
@@ -118,6 +120,7 @@ impl Cred {
     /// successful.
     ///
     /// [1]: https://www.kernel.org/pub/software/scm/git/docs/gitcredentials.html
+    #[cfg(feature = "cred")]
     pub fn credential_helper(
         config: &Config,
         url: &str,
@@ -189,6 +192,7 @@ impl Drop for Cred {
     }
 }
 
+#[cfg(feature = "cred")]
 impl CredentialHelper {
     /// Create a new credential helper object which will be used to probe git's
     /// local credential configuration.
@@ -292,6 +296,12 @@ impl CredentialHelper {
     // see https://www.kernel.org/pub/software/scm/git/docs/technical
     //                           /api-credentials.html#_credential_helpers
     fn add_command(&mut self, cmd: Option<&str>) {
+        fn is_absolute_path(path: &str) -> bool {
+            path.starts_with('/')
+                || path.starts_with('\\')
+                || cfg!(windows) && path.chars().nth(1).is_some_and(|x| x == ':')
+        }
+
         let cmd = match cmd {
             Some("") | None => return,
             Some(s) => s,
@@ -352,6 +362,9 @@ impl CredentialHelper {
         cmd: &str,
         username: &Option<String>,
     ) -> (Option<String>, Option<String>) {
+        use std::io::Write;
+        use std::process::{Command, Stdio};
+
         macro_rules! my_try( ($e:expr) => (
             match $e {
                 Ok(e) => e,
@@ -481,13 +494,8 @@ impl CredentialHelper {
     }
 }
 
-fn is_absolute_path(path: &str) -> bool {
-    path.starts_with('/')
-        || path.starts_with('\\')
-        || cfg!(windows) && path.chars().nth(1).is_some_and(|x| x == ':')
-}
-
 #[cfg(test)]
+#[cfg(feature = "cred")]
 mod test {
     use std::env;
     use std::fs::File;

src/lib.rs

@@ -88,7 +88,9 @@ pub use crate::buf::Buf;
 pub use crate::cherrypick::CherrypickOptions;
 pub use crate::commit::{Commit, Parents};
 pub use crate::config::{Config, ConfigEntries, ConfigEntry};
-pub use crate::cred::{Cred, CredentialHelper};
+pub use crate::cred::Cred;
+#[cfg(feature = "cred")]
+pub use crate::cred::CredentialHelper;
 pub use crate::describe::{Describe, DescribeFormatOptions, DescribeOptions};
 pub use crate::diff::{Deltas, Diff, DiffDelta, DiffFile, DiffOptions};
 pub use crate::diff::{DiffBinary, DiffBinaryFile, DiffBinaryKind, DiffPatchidOptions};