Merge branch 'jk/no-diff-emit-common' into maint

"git merge-tree" used to mishandle "both sides added" conflict with
its own "create a fake ancestor file that has the common parts of
what both sides have added and do a 3-way merge" logic; this has
been updated to use the usual "3-way merge with an empty blob as
the fake common ancestor file" approach used in the rest of the
system.

* jk/no-diff-emit-common:
  xdiff: drop XDL_EMIT_COMMON
  merge-tree: drop generate_common strategy
  merge-one-file: use empty blob for add/add base

Author: gitster

git-merge-one-file.sh

@@ -120,8 +120,7 @@ case "${1:-.}${2:-.}${3:-.}" in
 	case "$1" in
 	'')
 		echo "Added $4 in both, but differently."
-		orig=$(git-unpack-file $2)
-		create_virtual_base "$orig" "$src2"
+		orig=$(git-unpack-file e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
 		;;
 	*)
 		echo "Auto-merging $4"

merge-blobs.c

@@ -48,40 +48,6 @@ static void *three_way_filemerge(const char *path, mmfile_t *base, mmfile_t *our
 	return res.ptr;
 }
 
-static int common_outf(void *priv_, mmbuffer_t *mb, int nbuf)
-{
-	int i;
-	mmfile_t *dst = priv_;
-
-	for (i = 0; i < nbuf; i++) {
-		memcpy(dst->ptr + dst->size, mb[i].ptr, mb[i].size);
-		dst->size += mb[i].size;
-	}
-	return 0;
-}
-
-static int generate_common_file(mmfile_t *res, mmfile_t *f1, mmfile_t *f2)
-{
-	unsigned long size = f1->size < f2->size ? f1->size : f2->size;
-	void *ptr = xmalloc(size);
-	xpparam_t xpp;
-	xdemitconf_t xecfg;
-	xdemitcb_t ecb;
-
-	memset(&xpp, 0, sizeof(xpp));
-	xpp.flags = 0;
-	memset(&xecfg, 0, sizeof(xecfg));
-	xecfg.ctxlen = 3;
-	xecfg.flags = XDL_EMIT_COMMON;
-	ecb.outf = common_outf;
-
-	res->ptr = ptr;
-	res->size = 0;
-
-	ecb.priv = res;
-	return xdi_diff(f1, f2, &xpp, &xecfg, &ecb);
-}
-
 void *merge_blobs(const char *path, struct blob *base, struct blob *our, struct blob *their, unsigned long *size)
 {
 	void *res = NULL;
@@ -112,8 +78,8 @@ void *merge_blobs(const char *path, struct blob *base, struct blob *our, struct
 		if (fill_mmfile_blob(&common, base) < 0)
 			goto out_free_f2_f1;
 	} else {
-		if (generate_common_file(&common, &f1, &f2) < 0)
-			goto out_free_f2_f1;
+		common.ptr = xstrdup("");
+		common.size = 0;
 	}
 	res = three_way_filemerge(path, &common, &f1, &f2, size);
 	free_mmfile(&common);

xdiff/xdiff.h

@@ -42,7 +42,6 @@ extern "C" {
 #define XDF_IGNORE_BLANK_LINES (1 << 7)
 
 #define XDL_EMIT_FUNCNAMES (1 << 0)
-#define XDL_EMIT_COMMON (1 << 1)
 #define XDL_EMIT_FUNCCONTEXT (1 << 2)
 
 #define XDL_MMB_READONLY (1 << 0)

xdiff/xemit.c

@@ -120,21 +120,6 @@ static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)
 	return -1;
 }
 
-static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
-                           xdemitconf_t const *xecfg) {
-	xdfile_t *xdf = &xe->xdf2;
-	const char *rchg = xdf->rchg;
-	long ix;
-
-	for (ix = 0; ix < xdf->nrec; ix++) {
-		if (rchg[ix])
-			continue;
-		if (xdl_emit_record(xdf, ix, "", ecb))
-			return -1;
-	}
-	return 0;
-}
-
 struct func_line {
 	long len;
 	char buf[80];
@@ -170,9 +155,6 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 	long funclineprev = -1;
 	struct func_line func_line = { 0 };
 
-	if (xecfg->flags & XDL_EMIT_COMMON)
-		return xdl_emit_common(xe, xscr, ecb, xecfg);
-
 	for (xch = xscr; xch; xch = xche->next) {
 		xche = xdl_get_hunk(&xch, xecfg);
 		if (!xch)