fix: ignore empty core.askpass settings

This is the same as what `git` does, it's explicit per value, which
means that other paths might be flagged as empty automatically.

Author: Byron

gix/src/config/cache/util.rs

@@ -120,6 +120,10 @@ pub trait ApplyLeniency {
     fn with_leniency(self, is_lenient: bool) -> Self;
 }
 
+pub trait IgnoreEmptyPath {
+    fn ignore_empty(self) -> Self;
+}
+
 pub trait ApplyLeniencyDefault {
     fn with_lenient_default(self, is_lenient: bool) -> Self;
 }
@@ -138,6 +142,16 @@ impl<T, E> ApplyLeniency for Result<Option<T>, E> {
     }
 }
 
+impl IgnoreEmptyPath for Result<Option<std::borrow::Cow<'_, std::path::Path>>, gix_config::path::interpolate::Error> {
+    fn ignore_empty(self) -> Self {
+        match self {
+            Ok(maybe_path) => Ok(maybe_path),
+            Err(gix_config::path::interpolate::Error::Missing { .. }) => Ok(None),
+            Err(err) => Err(err),
+        }
+    }
+}
+
 impl<T, E> ApplyLeniencyDefault for Result<T, E>
 where
     T: Default,

gix/src/config/snapshot/credential_helpers.rs

@@ -2,6 +2,7 @@ use std::{borrow::Cow, convert::TryFrom};
 
 pub use error::Error;
 
+use crate::config::cache::util::IgnoreEmptyPath;
 use crate::{
     bstr::{ByteSlice, ByteVec},
     config::{
@@ -140,7 +141,8 @@ impl Snapshot<'_> {
         let prompt_options = gix_prompt::Options {
             askpass: self
                 .trusted_path(Core::ASKPASS.logical_name().as_str())
-                .transpose()?
+                .transpose()
+                .ignore_empty()?
                 .map(|c| Cow::Owned(c.into_owned())),
             ..Default::default()
         }

gix/tests/fixtures/make_remote_repos.sh

@@ -370,3 +370,8 @@ git clone one-commit-with-symref one-commit-with-symref-missing-branch
 (cd one-commit-with-symref-missing-branch
   git branch valid-locally
 )
+
+git init empty-core-askpass
+(cd empty-core-askpass
+  echo "    askpass =" >> .git/config
+)

gix/tests/repository/config/config_snapshot/credential_helpers.rs

@@ -1,3 +1,4 @@
+use crate::remote;
 use gix_testtools::Env;
 
 mod baseline {
@@ -205,3 +206,12 @@ fn invalid_urls_are_rejected_early() {
     baseline::works_but_we_dont_parse_invalid_url("ssh://host:21");
     baseline::works_but_we_dont_parse_invalid_url("git://host.org");
 }
+
+#[test]
+fn empty_core_askpass_is_ignored() -> crate::Result {
+    let repo = remote::repo("empty-core-askpass");
+    let _ = repo
+        .config_snapshot()
+        .credential_helpers("does-not-matter".try_into()?)?;
+    Ok(())
+}