Set +x in index in gix-worktree-stream basic fixture, adjust test

As in 470c76e, this updates tests to reflect the ability of Git
repositories to represent Unix-style executable permissions in an
index and commits, and the ability of gitoxide to operate on this,
on all platforms, including Windows where the filesystem itself
does not support this kind of executable permissons. Changes:

1. Adds a `git update-index --chmod=+x` command in the basic.sh
   fixture for gix-worktree-steam, so `dir/subtree/exe` is marked
   executable in the repository, even on Windows where the
   filesystem itself does not support Unix-style executable
   permissions and where, in Git Bash, `chmod +x` has no effect.

   This does not affect `extra-exe`, which is never staged. Since
   `extra-exe` is just an extra file in the working tree, it cannot
   be marked `+x` on Windows.

2. Updates the `paths_and_modes` assertion in
   `will_provide_all_information_and_respect_export_ignore` to
   assert the correct mode, with `+x` set, in the staged/committed
   file `dir/subtree/exe`.

   The `extra-exe` part of the assertion is unchanged in meaning,
   but the `expected_exe_mode` would only be used in that one
   place now, so this removes it and replaces it with the
   conditional expression for its value based on whether we are
   using Windows. While doing that refactoring, this also removes
   the `expected_link_mode` constant, which has unconditionally
   aliased `EntryKind::Link` since 93e088a (GitoxideLabs#1444).

These changes are directly analogous to (1) and (2) in 470c76e.
Here, they are made to the gix-worktree-stream tests, while in
470c76e they were made to the gix-archive tests (along with another
related change, in (3), for which there is nothing anlogous to be
done here).

For reference, with *this* commit's change (1) described above but
without *this* commit's change (2), the failure is:

    --- STDERR:              gix-worktree-stream::stream from_tree::will_provide_all_information_and_respect_export_ignore ---
        Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.45s
    thread 'from_tree::will_provide_all_information_and_respect_export_ignore' panicked at gix-worktree-stream\tests\stream.rs:119:9:
    assertion `left == right` failed
      left: [(".gitattributes", Blob, Sha1(45c160c35c17ad264b96431cceb9793160396e99)), ("a", Blob, Sha1(45b983be36b73c0788dc9cbcb76cbb80fc7bb057)), ("bigfile", Blob, Sha1(4995fde49ed64e043977e22539f66a0d372dd129)), ("symlink-to-a", Link, Sha1(2e65efe2a145dda7ee51d1741299f848e5bf752e)), ("dir/.gitattributes", Blob, Sha1(81b9a375276405703e05be6cecf0fc1c8b8eed64)), ("dir/b", Blob, Sha1(ab4a98190cf776b43cb0fe57cef231fb93fd07e6)), ("dir/subdir/exe", BlobExecutable, Sha1(e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)), ("dir/subdir/streamed", Blob, Sha1(08991f58f4de5d85b61c0f87f3ac053c79d0e739)), ("extra-file", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-bigfile", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-exe", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-dir-empty", Tree, Sha1(0000000000000000000000000000000000000000)), ("extra-dir/symlink-to-extra", Link, Sha1(0000000000000000000000000000000000000000))]
     right: [(".gitattributes", Blob, Sha1(45c160c35c17ad264b96431cceb9793160396e99)), ("a", Blob, Sha1(45b983be36b73c0788dc9cbcb76cbb80fc7bb057)), ("bigfile", Blob, Sha1(4995fde49ed64e043977e22539f66a0d372dd129)), ("symlink-to-a", Link, Sha1(2e65efe2a145dda7ee51d1741299f848e5bf752e)), ("dir/.gitattributes", Blob, Sha1(81b9a375276405703e05be6cecf0fc1c8b8eed64)), ("dir/b", Blob, Sha1(ab4a98190cf776b43cb0fe57cef231fb93fd07e6)), ("dir/subdir/exe", Blob, Sha1(e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)), ("dir/subdir/streamed", Blob, Sha1(08991f58f4de5d85b61c0f87f3ac053c79d0e739)), ("extra-file", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-bigfile", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-exe", Blob, Sha1(0000000000000000000000000000000000000000)), ("extra-dir-empty", Tree, Sha1(0000000000000000000000000000000000000000)), ("extra-dir/symlink-to-extra", Link, Sha1(0000000000000000000000000000000000000000))]
    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Author: EliahKagan

gix-worktree-stream/tests/fixtures/basic.sh

@@ -23,6 +23,7 @@ echo "/file-ignored export-ignore" >> .gitattributes
 dd if=/dev/zero of=bigfile bs=1024 count=156
 
 git add .
+git update-index --chmod=+x dir/subdir/exe
 git commit -m "init"
 
 echo "extra" > extra-file
@@ -32,4 +33,3 @@ ln -s ../extra-file extra-dir/symlink-to-extra
 dd if=/dev/zero of=extra-bigfile bs=1024 count=156
 
 git rev-parse @^{tree} > head.hex
-

gix-worktree-stream/tests/stream.rs

@@ -110,12 +110,6 @@ mod from_tree {
             }
         }
 
-        let expected_exe_mode = if cfg!(windows) {
-            EntryKind::Blob
-        } else {
-            EntryKind::BlobExecutable
-        };
-        let expected_link_mode = EntryKind::Link;
         assert_eq!(
             paths_and_modes,
             &[
@@ -136,7 +130,7 @@ mod from_tree {
                 ),
                 (
                     "symlink-to-a".into(),
-                    expected_link_mode,
+                    EntryKind::Link,
                     hex_to_id("2e65efe2a145dda7ee51d1741299f848e5bf752e")
                 ),
                 (
@@ -151,7 +145,7 @@ mod from_tree {
                 ),
                 (
                     "dir/subdir/exe".into(),
-                    expected_exe_mode,
+                    EntryKind::BlobExecutable,
                     hex_to_id("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391")
                 ),
                 (
@@ -171,7 +165,7 @@ mod from_tree {
                 ),
                 (
                     "extra-exe".into(),
-                    expected_exe_mode,
+                    if cfg!(windows) { EntryKind::Blob } else { EntryKind::BlobExecutable },
                     hex_to_id("0000000000000000000000000000000000000000")
                 ),
                 (
@@ -181,7 +175,7 @@ mod from_tree {
                 ),
                 (
                     "extra-dir/symlink-to-extra".into(),
-                    expected_link_mode,
+                    EntryKind::Link,
                     hex_to_id("0000000000000000000000000000000000000000")
                 )
             ]