merge: make the internal flags public

We made the flags that enable recursive merge internal, on the
assumption that nobody would want them and they're hard to reason about.
(Giving people an option that nobody wants is just extra noise.)

However, it made it hard for _us_ to reason about.  There's no good
reason to keep it private, let's just make it public and push that
cognitive load onto our poor users.  But they should expect it, they're
dealing with git, after all.

include/git2/merge.h

@@ -93,8 +93,13 @@ typedef enum {
 	 */
 	GIT_MERGE_NO_RECURSIVE = (1 << 3),
 
-	/* This flag is reserved for internal library use */
-	GIT_MERGE__INTERNAL_FLAG = (1 << 30)
+	/**
+	 * Treat this merge as if it is to produce the virtual base
+	 * of a recursive merge.  This will ensure that there are
+	 * no conflicts, any conflicting regions will keep conflict
+	 * markers in the merge result.
+	 */
+	GIT_MERGE_VIRTUAL_BASE = (1 << 4)
 } git_merge_flag_t;
 
 /**
@@ -167,8 +172,12 @@ typedef enum {
 	/** Create zdiff3 ("zealous diff3")-style files */
 	GIT_MERGE_FILE_STYLE_ZDIFF3 = (1 << 8),
 
-	/* This flag is reserved for internal library use */
-	GIT_MERGE_FILE__INTERNAL_FLAG = (1 << 30)
+	/**
+	 * Do not produce file conflicts when common regions have
+	 * changed; keep the conflict markers in the file and accept
+	 * that as the merge result.
+	 */
+	GIT_MERGE_FILE_ACCEPT_CONFLICTS = (1 << 9)
 } git_merge_file_flag_t;
 
 #define GIT_MERGE_CONFLICT_MARKER_SIZE	7

src/merge.c

@@ -2116,11 +2116,11 @@ int git_merge__iterators(
 	file_opts.flags = opts.file_flags;
 
 	/* use the git-inspired labels when virtual base building */
-	if (opts.flags & GIT_MERGE__VIRTUAL_BASE) {
+	if (opts.flags & GIT_MERGE_VIRTUAL_BASE) {
 		file_opts.ancestor_label = "merged common ancestors";
 		file_opts.our_label = "Temporary merge branch 1";
 		file_opts.their_label = "Temporary merge branch 2";
-		file_opts.flags |= GIT_MERGE_FILE__CONFLICTED;
+		file_opts.flags |= GIT_MERGE_FILE_ACCEPT_CONFLICTS;
 		file_opts.marker_size = GIT_MERGE_CONFLICT_MARKER_SIZE + 2;
 	}
 
@@ -2280,7 +2280,7 @@ static int create_virtual_base(
 		memcpy(&virtual_opts, opts, sizeof(git_merge_options));
 
 	virtual_opts.flags &= ~GIT_MERGE_FAIL_ON_CONFLICT;
-	virtual_opts.flags |= GIT_MERGE__VIRTUAL_BASE;
+	virtual_opts.flags |= GIT_MERGE_VIRTUAL_BASE;
 
 	if ((merge_annotated_commits(&index, NULL, repo, one, two,
 			recursion_level + 1, &virtual_opts)) < 0)

src/merge.h

@@ -25,16 +25,6 @@
 #define GIT_MERGE_DEFAULT_RENAME_THRESHOLD	50
 #define GIT_MERGE_DEFAULT_TARGET_LIMIT		1000
 
-
-/** Internal merge flags. */
-
-/** The merge is for a virtual base in a recursive merge. */
-#define GIT_MERGE__VIRTUAL_BASE (GIT_MERGE__INTERNAL_FLAG)
-
-/** Accept the conflict file, staging it as the merge result. */
-#define GIT_MERGE_FILE__CONFLICTED (GIT_MERGE_FILE__INTERNAL_FLAG)
-
-
 /** Types of changes when files are merged from branch to branch. */
 typedef enum {
 	/* No conflict - a change only occurs in one branch. */

src/merge_driver.c

@@ -93,7 +93,7 @@ int git_merge_driver__builtin_apply(
 		goto done;
 
 	if (!result.automergeable &&
-		!(file_opts.flags & GIT_MERGE_FILE__CONFLICTED)) {
+		!(file_opts.flags & GIT_MERGE_FILE_ACCEPT_CONFLICTS)) {
 		error = GIT_EMERGECONFLICT;
 		goto done;
 	}