fix(repo): preserve trailing whitespace in blamed line content

`Repo.blame` built each blamed line with `line_bytes.rstrip().decode(defenc)`
and then stripped the leading tab, but a `git blame -p` content line is a
leading tab, the blamed line's exact bytes, and git's own terminating line
feed. `rstrip` therefore dropped a line's trailing spaces and tabs, emptied a
whitespace-only line, and removed the carriage return of a CRLF line, so the
content returned by `repo.blame()` differed from both the file and
`git blame`. A caller that reconstructs or compares file content from blame,
for example to find the commit that introduced an exact line, was handed
altered text.

Recover the exact bytes instead: drop the leading tab and only git's trailing
line feed, then decode. Binary lines and the hexsha/header parsing are
unchanged, so the only behavior change is that blamed lines keep their
original trailing whitespace and carriage returns.

Adds `tests/fixtures/blame-content.sh` and `test_blame_preserves_line_content`
in `test/test_repo.py`, which fail before the change
(`['alpha', 'beta', '', 'crlf', 'gamma']`) and pass after
(`['alpha   ', 'beta', '\t', 'crlf\r', 'gamma']`) on both the `cli` and `gix`
backends. `ruff check`, `ruff format --check` and `mypy` pass on the touched
files. The repository's pre-existing shallow-clone failures occur identically
with and without this change.

Agent-Model: claude-opus-4-8

Author: Keerthana-64

git/repo/base.py

@@ -1550,9 +1550,15 @@ class InfoTD(TypedDict, total=False):
                             if blames[-1][1] is not None:
                                 line: str | bytes
                                 if not is_binary:
-                                    if line_str and line_str[0] == "\t":
-                                        line_str = line_str[1:]
-                                    line = line_str
+                                    # Recover the exact line bytes. A porcelain content
+                                    # line is a leading tab, the blamed line's bytes, and
+                                    # git's terminating line feed, so rstrip() would drop
+                                    # the line's own trailing whitespace and the carriage
+                                    # return of a CRLF line.
+                                    content = line_bytes[1:] if line_bytes[:1] == b"\t" else line_bytes
+                                    if content.endswith(b"\n"):
+                                        content = content[:-1]
+                                    line = content.decode(defenc)
                                 else:
                                     line = line_bytes
                                     # NOTE: We are actually parsing lines out of binary

test/test_repo.py

@@ -784,6 +784,12 @@ def test_blame_incremental_preserves_historical_paths(self):
                     )
                     self.assertEqual(list(repo.blame("HEAD", "current.txt", incremental=True)), entries)
 
+    def test_blame_preserves_line_content(self):
+        """Blame returns each line's exact bytes, not a whitespace-stripped version."""
+        with fixture_repo("blame-content.sh") as repo:
+            lines = [line for _commit, blamed in repo.blame("HEAD", "file.txt") for line in blamed]
+            self.assertEqual(lines, ["alpha   ", "beta", "\t", "crlf\r", "gamma"])
+
     @mock.patch.object(Git, "_call_process")
     def test_blame_complex_revision(self, git):
         git.return_value = fixture("blame_complex_revision")

tests/fixtures/blame-content.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -eu
+git init -q --initial-branch=main repo
+cd repo
+# Build the blob directly so trailing whitespace, a whitespace-only line, and a
+# CRLF line survive fixture creation on every platform.
+blob=$(printf 'alpha   \nbeta\n\t\ncrlf\r\ngamma\n' | git hash-object -w --stdin)
+tree=$(printf '100644 blob %s\tfile.txt\0' "$blob" | git mktree -z)
+commit=$(git -c user.name=A -c user.email=a@example.com commit-tree "$tree" -m content)
+git update-ref refs/heads/main "$commit"