diff: enable the indent heuristic by default

The diff option is now reversed and can be used to get back to the previous
form.

3 files changed, 14 insertions, 9 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc8f87c0c..3aa785222 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,9 +10,12 @@ v0.26 + 1
   caller for the case-insensitive portions of the key (existing sections are
   used even if they don't match).
 
-* There is a new diff option, `GIT_DIFF_INDENT_HEURISTIC` which activates a
-  heuristic which takes into account whitespace and indentation in order to
-  produce better diffs when dealing with ambiguous diff hunks.
+* We now default to using the new diff heuristic (from the git tool) which takes
+  into account whitespace and indentation in order to produce better diffs when
+  dealing with ambiguous diff hunks.
+
+* There is a new diff option, `GIT_DIFF_DISABLE_INDENT_HEURISTIC` which disables
+  the indent-based heuristic to get back to the previous behaviour.
 
 ### API additions
 
diff --git a/include/git2/diff.h b/include/git2/diff.h
index 99a94bb6d..93f9cb0f7 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -207,11 +207,11 @@ typedef enum {
 	 */
 	GIT_DIFF_SHOW_BINARY = (1 << 30),
 
-	/** Use a heuristic that takes indentation and whitespace into account
-	 * which generally can produce better diffs when dealing with ambiguous
-	 * diff hunks.
+	/** Disable the use of a heuristic that takes indentation and whitespace
+	 * into account which generally can produce better diffs when dealing
+	 * with ambiguous diff hunks.
 	 */
-	GIT_DIFF_INDENT_HEURISTIC = (1 << 31),
+	GIT_DIFF_DISABLE_INDENT_HEURISTIC = (1 << 31),
 } git_diff_option_t;
 
 /**
diff --git a/src/diff_xdiff.c b/src/diff_xdiff.c
index 701eb1b5f..b101b0741 100644
--- a/src/diff_xdiff.c
+++ b/src/diff_xdiff.c
@@ -233,14 +233,16 @@ void git_xdiff_init(git_xdiff_output *xo, const git_diff_options *opts)
 	xo->config.ctxlen = opts ? opts->context_lines : 3;
 	xo->config.interhunkctxlen = opts ? opts->interhunk_lines : 0;
 
+	xo->params.flags |= XDF_INDENT_HEURISTIC;
+
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE)
 		xo->params.flags |= XDF_WHITESPACE_FLAGS;
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE_CHANGE)
 		xo->params.flags |= XDF_IGNORE_WHITESPACE_CHANGE;
 	if (flags & GIT_DIFF_IGNORE_WHITESPACE_EOL)
 		xo->params.flags |= XDF_IGNORE_WHITESPACE_AT_EOL;
-	if (flags & GIT_DIFF_INDENT_HEURISTIC)
-		xo->params.flags |= XDF_INDENT_HEURISTIC;
+	if (flags & GIT_DIFF_DISABLE_INDENT_HEURISTIC)
+		xo->params.flags &= ~XDF_INDENT_HEURISTIC;
 
 	if (flags & GIT_DIFF_PATIENCE)
 		xo->params.flags |= XDF_PATIENCE_DIFF;