Merge branch 'jc/apply-trailing-blank-removal'
[git/git.git] / builtin / apply.c
index f8202e3..6c11e8b 100644 (file)
@@ -16,6 +16,9 @@
 #include "dir.h"
 #include "diff.h"
 #include "parse-options.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "rerere.h"
 
 /*
  *  --check turns on checking that the working tree matches the
@@ -46,6 +49,7 @@ static int apply_with_reject;
 static int apply_verbosely;
 static int allow_overlap;
 static int no_add;
+static int threeway;
 static const char *fake_ancestor;
 static int line_termination = '\n';
 static unsigned int p_context = UINT_MAX;
@@ -192,12 +196,17 @@ struct patch {
        unsigned int is_copy:1;
        unsigned int is_rename:1;
        unsigned int recount:1;
+       unsigned int conflicted_threeway:1;
+       unsigned int direct_to_threeway:1;
        struct fragment *fragments;
        char *result;
        size_t resultsize;
        char old_sha1_prefix[41];
        char new_sha1_prefix[41];
        struct patch *next;
+
+       /* three-way fallback result */
+       unsigned char threeway_stage[3][20];
 };
 
 static void free_fragment_list(struct fragment *list)
@@ -370,8 +379,8 @@ static void prepare_image(struct image *image, char *buf, size_t len,
 static void clear_image(struct image *image)
 {
        free(image->buf);
-       image->buf = NULL;
-       image->len = 0;
+       free(image->line_allocated);
+       memset(image, 0, sizeof(*image));
 }
 
 /* fmt must contain _one_ %s and no other substitution */
@@ -2965,20 +2974,17 @@ static int apply_fragments(struct image *img, struct patch *patch)
        return 0;
 }
 
-static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
+static int read_blob_object(struct strbuf *buf, const unsigned char *sha1, unsigned mode)
 {
-       if (!ce)
-               return 0;
-
-       if (S_ISGITLINK(ce->ce_mode)) {
+       if (S_ISGITLINK(mode)) {
                strbuf_grow(buf, 100);
-               strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(ce->sha1));
+               strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(sha1));
        } else {
                enum object_type type;
                unsigned long sz;
                char *result;
 
-               result = read_sha1_file(ce->sha1, &type, &sz);
+               result = read_sha1_file(sha1, &type, &sz);
                if (!result)
                        return -1;
                /* XXX read_sha1_file NUL-terminates */
@@ -2987,6 +2993,13 @@ static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
        return 0;
 }
 
+static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
+{
+       if (!ce)
+               return 0;
+       return read_blob_object(buf, ce->sha1, ce->ce_mode);
+}
+
 static struct patch *in_fn_table(const char *name)
 {
        struct string_list_item *item;
@@ -3005,9 +3018,15 @@ static struct patch *in_fn_table(const char *name)
  * item->util in the filename table records the status of the path.
  * Usually it points at a patch (whose result records the contents
  * of it after applying it), but it could be PATH_WAS_DELETED for a
- * path that a previously applied patch has already removed.
+ * path that a previously applied patch has already removed, or
+ * PATH_TO_BE_DELETED for a path that a later patch would remove.
+ *
+ * The latter is needed to deal with a case where two paths A and B
+ * are swapped by first renaming A to B and then renaming B to A;
+ * moving A to B should not be prevented due to presense of B as we
+ * will remove it in a later patch.
  */
- #define PATH_TO_BE_DELETED ((struct patch *) -2)
+#define PATH_TO_BE_DELETED ((struct patch *) -2)
 #define PATH_WAS_DELETED ((struct patch *) -1)
 
 static int to_be_deleted(struct patch *patch)
@@ -3059,127 +3078,324 @@ static void prepare_fn_table(struct patch *patch)
        }
 }
 
-static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
+static int checkout_target(struct cache_entry *ce, struct stat *st)
+{
+       struct checkout costate;
+
+       memset(&costate, 0, sizeof(costate));
+       costate.base_dir = "";
+       costate.refresh_cache = 1;
+       if (checkout_entry(ce, &costate, NULL) || lstat(ce->name, st))
+               return error(_("cannot checkout %s"), ce->name);
+       return 0;
+}
+
+static struct patch *previous_patch(struct patch *patch, int *gone)
+{
+       struct patch *previous;
+
+       *gone = 0;
+       if (patch->is_copy || patch->is_rename)
+               return NULL; /* "git" patches do not depend on the order */
+
+       previous = in_fn_table(patch->old_name);
+       if (!previous)
+               return NULL;
+
+       if (to_be_deleted(previous))
+               return NULL; /* the deletion hasn't happened yet */
+
+       if (was_deleted(previous))
+               *gone = 1;
+
+       return previous;
+}
+
+static int verify_index_match(struct cache_entry *ce, struct stat *st)
+{
+       if (S_ISGITLINK(ce->ce_mode)) {
+               if (!S_ISDIR(st->st_mode))
+                       return -1;
+               return 0;
+       }
+       return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+}
+
+#define SUBMODULE_PATCH_WITHOUT_INDEX 1
+
+static int load_patch_target(struct strbuf *buf,
+                            struct cache_entry *ce,
+                            struct stat *st,
+                            const char *name,
+                            unsigned expected_mode)
+{
+       if (cached) {
+               if (read_file_or_gitlink(ce, buf))
+                       return error(_("read of %s failed"), name);
+       } else if (name) {
+               if (S_ISGITLINK(expected_mode)) {
+                       if (ce)
+                               return read_file_or_gitlink(ce, buf);
+                       else
+                               return SUBMODULE_PATCH_WITHOUT_INDEX;
+               } else {
+                       if (read_old_data(st, name, buf))
+                               return error(_("read of %s failed"), name);
+               }
+       }
+       return 0;
+}
+
+/*
+ * We are about to apply "patch"; populate the "image" with the
+ * current version we have, from the working tree or from the index,
+ * depending on the situation e.g. --cached/--index.  If we are
+ * applying a non-git patch that incrementally updates the tree,
+ * we read from the result of a previous diff.
+ */
+static int load_preimage(struct image *image,
+                        struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
        struct strbuf buf = STRBUF_INIT;
-       struct image image;
        size_t len;
        char *img;
-       struct patch *tpatch;
+       struct patch *previous;
+       int status;
 
-       if (!(patch->is_copy || patch->is_rename) &&
-           (tpatch = in_fn_table(patch->old_name)) != NULL && !to_be_deleted(tpatch)) {
-               if (was_deleted(tpatch)) {
-                       return error(_("patch %s has been renamed/deleted"),
-                               patch->old_name);
-               }
+       previous = previous_patch(patch, &status);
+       if (status)
+               return error(_("path %s has been renamed/deleted"),
+                            patch->old_name);
+       if (previous) {
                /* We have a patched copy in memory; use that. */
-               strbuf_add(&buf, tpatch->result, tpatch->resultsize);
-       } else if (cached) {
-               if (read_file_or_gitlink(ce, &buf))
+               strbuf_add(&buf, previous->result, previous->resultsize);
+       } else {
+               status = load_patch_target(&buf, ce, st,
+                                          patch->old_name, patch->old_mode);
+               if (status < 0)
+                       return status;
+               else if (status == SUBMODULE_PATCH_WITHOUT_INDEX) {
+                       /*
+                        * There is no way to apply subproject
+                        * patch without looking at the index.
+                        * NEEDSWORK: shouldn't this be flagged
+                        * as an error???
+                        */
+                       free_fragment_list(patch->fragments);
+                       patch->fragments = NULL;
+               } else if (status) {
                        return error(_("read of %s failed"), patch->old_name);
-       } else if (patch->old_name) {
-               if (S_ISGITLINK(patch->old_mode)) {
-                       if (ce) {
-                               read_file_or_gitlink(ce, &buf);
-                       } else {
-                               /*
-                                * There is no way to apply subproject
-                                * patch without looking at the index.
-                                * NEEDSWORK: shouldn't this be flagged
-                                * as an error???
-                                */
-                               free_fragment_list(patch->fragments);
-                               patch->fragments = NULL;
-                       }
-               } else {
-                       if (read_old_data(st, patch->old_name, &buf))
-                               return error(_("read of %s failed"), patch->old_name);
                }
        }
 
        img = strbuf_detach(&buf, &len);
-       prepare_image(&image, img, len, !patch->is_binary);
+       prepare_image(image, img, len, !patch->is_binary);
+       return 0;
+}
 
-       if (apply_fragments(&image, patch) < 0)
-               return -1; /* note with --reject this succeeds. */
-       patch->result = image.buf;
-       patch->resultsize = image.len;
-       add_to_fn_table(patch);
-       free(image.line_allocated);
+static int three_way_merge(struct image *image,
+                          char *path,
+                          const unsigned char *base,
+                          const unsigned char *ours,
+                          const unsigned char *theirs)
+{
+       mmfile_t base_file, our_file, their_file;
+       mmbuffer_t result = { NULL };
+       int status;
 
-       if (0 < patch->is_delete && patch->resultsize)
-               return error(_("removal patch leaves file contents"));
+       read_mmblob(&base_file, base);
+       read_mmblob(&our_file, ours);
+       read_mmblob(&their_file, theirs);
+       status = ll_merge(&result, path,
+                         &base_file, "base",
+                         &our_file, "ours",
+                         &their_file, "theirs", NULL);
+       free(base_file.ptr);
+       free(our_file.ptr);
+       free(their_file.ptr);
+       if (status < 0 || !result.ptr) {
+               free(result.ptr);
+               return -1;
+       }
+       clear_image(image);
+       image->buf = result.ptr;
+       image->len = result.size;
 
+       return status;
+}
+
+/*
+ * When directly falling back to add/add three-way merge, we read from
+ * the current contents of the new_name.  In no cases other than that
+ * this function will be called.
+ */
+static int load_current(struct image *image, struct patch *patch)
+{
+       struct strbuf buf = STRBUF_INIT;
+       int status, pos;
+       size_t len;
+       char *img;
+       struct stat st;
+       struct cache_entry *ce;
+       char *name = patch->new_name;
+       unsigned mode = patch->new_mode;
+
+       if (!patch->is_new)
+               die("BUG: patch to %s is not a creation", patch->old_name);
+
+       pos = cache_name_pos(name, strlen(name));
+       if (pos < 0)
+               return error(_("%s: does not exist in index"), name);
+       ce = active_cache[pos];
+       if (lstat(name, &st)) {
+               if (errno != ENOENT)
+                       return error(_("%s: %s"), name, strerror(errno));
+               if (checkout_target(ce, &st))
+                       return -1;
+       }
+       if (verify_index_match(ce, &st))
+               return error(_("%s: does not match index"), name);
+
+       status = load_patch_target(&buf, ce, &st, name, mode);
+       if (status < 0)
+               return status;
+       else if (status)
+               return -1;
+       img = strbuf_detach(&buf, &len);
+       prepare_image(image, img, len, !patch->is_binary);
        return 0;
 }
 
-static int check_to_create_blob(const char *new_name, int ok_if_exists)
+static int try_threeway(struct image *image, struct patch *patch,
+                       struct stat *st, struct cache_entry *ce)
 {
-       struct stat nst;
-       if (!lstat(new_name, &nst)) {
-               if (S_ISDIR(nst.st_mode) || ok_if_exists)
-                       return 0;
-               /*
-                * A leading component of new_name might be a symlink
-                * that is going to be removed with this patch, but
-                * still pointing at somewhere that has the path.
-                * In such a case, path "new_name" does not exist as
-                * far as git is concerned.
-                */
-               if (has_symlink_leading_path(new_name, strlen(new_name)))
-                       return 0;
+       unsigned char pre_sha1[20], post_sha1[20], our_sha1[20];
+       struct strbuf buf = STRBUF_INIT;
+       size_t len;
+       int status;
+       char *img;
+       struct image tmp_image;
+
+       /* No point falling back to 3-way merge in these cases */
+       if (patch->is_delete ||
+           S_ISGITLINK(patch->old_mode) || S_ISGITLINK(patch->new_mode))
+               return -1;
 
-               return error(_("%s: already exists in working directory"), new_name);
+       /* Preimage the patch was prepared for */
+       if (patch->is_new)
+               write_sha1_file("", 0, blob_type, pre_sha1);
+       else if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
+                read_blob_object(&buf, pre_sha1, patch->old_mode))
+               return error("repository lacks the necessary blob to fall back on 3-way merge.");
+
+       fprintf(stderr, "Falling back to three-way merge...\n");
+
+       img = strbuf_detach(&buf, &len);
+       prepare_image(&tmp_image, img, len, 1);
+       /* Apply the patch to get the post image */
+       if (apply_fragments(&tmp_image, patch) < 0) {
+               clear_image(&tmp_image);
+               return -1;
+       }
+       /* post_sha1[] is theirs */
+       write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, post_sha1);
+       clear_image(&tmp_image);
+
+       /* our_sha1[] is ours */
+       if (patch->is_new) {
+               if (load_current(&tmp_image, patch))
+                       return error("cannot read the current contents of '%s'",
+                                    patch->new_name);
+       } else {
+               if (load_preimage(&tmp_image, patch, st, ce))
+                       return error("cannot read the current contents of '%s'",
+                                    patch->old_name);
+       }
+       write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, our_sha1);
+       clear_image(&tmp_image);
+
+       /* in-core three-way merge between post and our using pre as base */
+       status = three_way_merge(image, patch->new_name,
+                                pre_sha1, our_sha1, post_sha1);
+       if (status < 0) {
+               fprintf(stderr, "Failed to fall back on three-way merge...\n");
+               return status;
+       }
+
+       if (status) {
+               patch->conflicted_threeway = 1;
+               if (patch->is_new)
+                       hashclr(patch->threeway_stage[0]);
+               else
+                       hashcpy(patch->threeway_stage[0], pre_sha1);
+               hashcpy(patch->threeway_stage[1], our_sha1);
+               hashcpy(patch->threeway_stage[2], post_sha1);
+               fprintf(stderr, "Applied patch to '%s' with conflicts.\n", patch->new_name);
+       } else {
+               fprintf(stderr, "Applied patch to '%s' cleanly.\n", patch->new_name);
        }
-       else if ((errno != ENOENT) && (errno != ENOTDIR))
-               return error("%s: %s", new_name, strerror(errno));
        return 0;
 }
 
-static int verify_index_match(struct cache_entry *ce, struct stat *st)
+static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
-       if (S_ISGITLINK(ce->ce_mode)) {
-               if (!S_ISDIR(st->st_mode))
+       struct image image;
+
+       if (load_preimage(&image, patch, st, ce) < 0)
+               return -1;
+
+       if (patch->direct_to_threeway ||
+           apply_fragments(&image, patch) < 0) {
+               /* Note: with --reject, apply_fragments() returns 0 */
+               if (!threeway || try_threeway(&image, patch, st, ce) < 0)
                        return -1;
-               return 0;
        }
-       return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+       patch->result = image.buf;
+       patch->resultsize = image.len;
+       add_to_fn_table(patch);
+       free(image.line_allocated);
+
+       if (0 < patch->is_delete && patch->resultsize)
+               return error(_("removal patch leaves file contents"));
+
+       return 0;
 }
 
+/*
+ * If "patch" that we are looking at modifies or deletes what we have,
+ * we would want it not to lose any local modification we have, either
+ * in the working tree or in the index.
+ *
+ * This also decides if a non-git patch is a creation patch or a
+ * modification to an existing empty file.  We do not check the state
+ * of the current tree for a creation patch in this function; the caller
+ * check_patch() separately makes sure (and errors out otherwise) that
+ * the path the patch creates does not exist in the current tree.
+ */
 static int check_preimage(struct patch *patch, struct cache_entry **ce, struct stat *st)
 {
        const char *old_name = patch->old_name;
-       struct patch *tpatch = NULL;
-       int stat_ret = 0;
+       struct patch *previous = NULL;
+       int stat_ret = 0, status;
        unsigned st_mode = 0;
 
-       /*
-        * Make sure that we do not have local modifications from the
-        * index when we are looking at the index.  Also make sure
-        * we have the preimage file to be patched in the work tree,
-        * unless --cached, which tells git to apply only in the index.
-        */
        if (!old_name)
                return 0;
 
        assert(patch->is_new <= 0);
+       previous = previous_patch(patch, &status);
 
-       if (!(patch->is_copy || patch->is_rename) &&
-           (tpatch = in_fn_table(old_name)) != NULL && !to_be_deleted(tpatch)) {
-               if (was_deleted(tpatch))
-                       return error(_("%s: has been deleted/renamed"), old_name);
-               st_mode = tpatch->new_mode;
+       if (status)
+               return error(_("path %s has been renamed/deleted"), old_name);
+       if (previous) {
+               st_mode = previous->new_mode;
        } else if (!cached) {
                stat_ret = lstat(old_name, st);
                if (stat_ret && errno != ENOENT)
                        return error(_("%s: %s"), old_name, strerror(errno));
        }
 
-       if (to_be_deleted(tpatch))
-               tpatch = NULL;
-
-       if (check_index && !tpatch) {
+       if (check_index && !previous) {
                int pos = cache_name_pos(old_name, strlen(old_name));
                if (pos < 0) {
                        if (patch->is_new < 0)
@@ -3188,13 +3404,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
                }
                *ce = active_cache[pos];
                if (stat_ret < 0) {
-                       struct checkout costate;
-                       /* checkout */
-                       memset(&costate, 0, sizeof(costate));
-                       costate.base_dir = "";
-                       costate.refresh_cache = 1;
-                       if (checkout_entry(*ce, &costate, NULL) ||
-                           lstat(old_name, st))
+                       if (checkout_target(*ce, st))
                                return -1;
                }
                if (!cached && verify_index_match(*ce, st))
@@ -3207,7 +3417,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
                return error(_("%s: %s"), old_name, strerror(errno));
        }
 
-       if (!cached && !tpatch)
+       if (!cached && !previous)
                st_mode = ce_mode_from_stat(*ce, st->st_mode);
 
        if (patch->is_new < 0)
@@ -3231,6 +3441,41 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
        return 0;
 }
 
+
+#define EXISTS_IN_INDEX 1
+#define EXISTS_IN_WORKTREE 2
+
+static int check_to_create(const char *new_name, int ok_if_exists)
+{
+       struct stat nst;
+
+       if (check_index &&
+           cache_name_pos(new_name, strlen(new_name)) >= 0 &&
+           !ok_if_exists)
+               return EXISTS_IN_INDEX;
+       if (cached)
+               return 0;
+
+       if (!lstat(new_name, &nst)) {
+               if (S_ISDIR(nst.st_mode) || ok_if_exists)
+                       return 0;
+               /*
+                * A leading component of new_name might be a symlink
+                * that is going to be removed with this patch, but
+                * still pointing at somewhere that has the path.
+                * In such a case, path "new_name" does not exist as
+                * far as git is concerned.
+                */
+               if (has_symlink_leading_path(new_name, strlen(new_name)))
+                       return 0;
+
+               return EXISTS_IN_WORKTREE;
+       } else if ((errno != ENOENT) && (errno != ENOTDIR)) {
+               return error("%s: %s", new_name, strerror(errno));
+       }
+       return 0;
+}
+
 /*
  * Check and apply the patch in-core; leave the result in patch->result
  * for the caller to write it out to the final destination.
@@ -3253,31 +3498,45 @@ static int check_patch(struct patch *patch)
                return status;
        old_name = patch->old_name;
 
+       /*
+        * A type-change diff is always split into a patch to delete
+        * old, immediately followed by a patch to create new (see
+        * diff.c::run_diff()); in such a case it is Ok that the entry
+        * to be deleted by the previous patch is still in the working
+        * tree and in the index.
+        *
+        * A patch to swap-rename between A and B would first rename A
+        * to B and then rename B to A.  While applying the first one,
+        * the presense of B should not stop A from getting renamed to
+        * B; ask to_be_deleted() about the later rename.  Removal of
+        * B and rename from A to B is handled the same way by asking
+        * was_deleted().
+        */
        if ((tpatch = in_fn_table(new_name)) &&
-                       (was_deleted(tpatch) || to_be_deleted(tpatch)))
-               /*
-                * A type-change diff is always split into a patch to
-                * delete old, immediately followed by a patch to
-                * create new (see diff.c::run_diff()); in such a case
-                * it is Ok that the entry to be deleted by the
-                * previous patch is still in the working tree and in
-                * the index.
-                */
+           (was_deleted(tpatch) || to_be_deleted(tpatch)))
                ok_if_exists = 1;
        else
                ok_if_exists = 0;
 
        if (new_name &&
            ((0 < patch->is_new) | (0 < patch->is_rename) | patch->is_copy)) {
-               if (check_index &&
-                   cache_name_pos(new_name, strlen(new_name)) >= 0 &&
-                   !ok_if_exists)
+               int err = check_to_create(new_name, ok_if_exists);
+
+               if (err && threeway) {
+                       patch->direct_to_threeway = 1;
+               } else switch (err) {
+               case 0:
+                       break; /* happy */
+               case EXISTS_IN_INDEX:
                        return error(_("%s: already exists in index"), new_name);
-               if (!cached) {
-                       int err = check_to_create_blob(new_name, ok_if_exists);
-                       if (err)
-                               return err;
+                       break;
+               case EXISTS_IN_WORKTREE:
+                       return error(_("%s: already exists in working directory"),
+                                    new_name);
+               default:
+                       return err;
                }
+
                if (!patch->new_mode) {
                        if (0 < patch->is_new)
                                patch->new_mode = S_IFREG | 0644;
@@ -3358,7 +3617,7 @@ static void build_fake_ancestor(struct patch *list, const char *filename)
                name = patch->old_name ? patch->old_name : patch->new_name;
                if (0 < patch->is_new)
                        continue;
-               else if (get_sha1(patch->old_sha1_prefix, sha1))
+               else if (get_sha1_blob(patch->old_sha1_prefix, sha1))
                        /* git diff has no index line for mode/type changes */
                        if (!patch->lines_added && !patch->lines_deleted) {
                                if (get_current_sha1(patch->old_name, sha1))
@@ -3538,7 +3797,8 @@ static void add_index_file(const char *path, unsigned mode, void *buf, unsigned
        ce = xcalloc(1, ce_size);
        memcpy(ce->name, path, namelen);
        ce->ce_mode = create_ce_mode(mode);
-       ce->ce_flags = namelen;
+       ce->ce_flags = create_ce_flags(0);
+       ce->ce_namelen = namelen;
        if (S_ISGITLINK(mode)) {
                const char *s = buf;
 
@@ -3640,6 +3900,33 @@ static void create_one_file(char *path, unsigned mode, const char *buf, unsigned
        die_errno(_("unable to write file '%s' mode %o"), path, mode);
 }
 
+static void add_conflicted_stages_file(struct patch *patch)
+{
+       int stage, namelen;
+       unsigned ce_size, mode;
+       struct cache_entry *ce;
+
+       if (!update_index)
+               return;
+       namelen = strlen(patch->new_name);
+       ce_size = cache_entry_size(namelen);
+       mode = patch->new_mode ? patch->new_mode : (S_IFREG | 0644);
+
+       remove_file_from_cache(patch->new_name);
+       for (stage = 1; stage < 4; stage++) {
+               if (is_null_sha1(patch->threeway_stage[stage - 1]))
+                       continue;
+               ce = xcalloc(1, ce_size);
+               memcpy(ce->name, patch->new_name, namelen);
+               ce->ce_mode = create_ce_mode(mode);
+               ce->ce_flags = create_ce_flags(stage);
+               ce->ce_namelen = namelen;
+               hashcpy(ce->sha1, patch->threeway_stage[stage - 1]);
+               if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
+                       die(_("unable to add cache entry for %s"), patch->new_name);
+       }
+}
+
 static void create_file(struct patch *patch)
 {
        char *path = patch->new_name;
@@ -3650,7 +3937,11 @@ static void create_file(struct patch *patch)
        if (!mode)
                mode = S_IFREG | 0644;
        create_one_file(path, mode, buf, size);
-       add_index_file(path, mode, buf, size);
+
+       if (patch->conflicted_threeway)
+               add_conflicted_stages_file(patch);
+       else
+               add_index_file(path, mode, buf, size);
 }
 
 /* phase zero is to remove, phase one is to create */
@@ -3752,6 +4043,7 @@ static int write_out_results(struct patch *list)
        int phase;
        int errs = 0;
        struct patch *l;
+       struct string_list cpath = STRING_LIST_INIT_DUP;
 
        for (phase = 0; phase < 2; phase++) {
                l = list;
@@ -3760,12 +4052,30 @@ static int write_out_results(struct patch *list)
                                errs = 1;
                        else {
                                write_out_one_result(l, phase);
-                               if (phase == 1 && write_out_one_reject(l))
-                                       errs = 1;
+                               if (phase == 1) {
+                                       if (write_out_one_reject(l))
+                                               errs = 1;
+                                       if (l->conflicted_threeway) {
+                                               string_list_append(&cpath, l->new_name);
+                                               errs = 1;
+                                       }
+                               }
                        }
                        l = l->next;
                }
        }
+
+       if (cpath.nr) {
+               struct string_list_item *item;
+
+               sort_string_list(&cpath);
+               for_each_string_list_item(item, &cpath)
+                       fprintf(stderr, "U %s\n", item->string);
+               string_list_clear(&cpath, 0);
+
+               rerere(0);
+       }
+
        return errs;
 }
 
@@ -3888,8 +4198,12 @@ static int apply_patch(int fd, const char *filename, int options)
            !apply_with_reject)
                exit(1);
 
-       if (apply && write_out_results(list))
-               exit(1);
+       if (apply && write_out_results(list)) {
+               if (apply_with_reject)
+                       exit(1);
+               /* with --3way, we still need to write the index out */
+               return 1;
+       }
 
        if (fake_ancestor)
                build_fake_ancestor(list, fake_ancestor);
@@ -4011,7 +4325,7 @@ int cmd_apply(int argc, const char **argv, const char *prefix_)
                OPT_NOOP_NOARG(0, "allow-binary-replacement"),
                OPT_NOOP_NOARG(0, "binary"),
                OPT_BOOLEAN(0, "numstat", &numstat,
-                       N_("shows number of added and deleted lines in decimal notation")),
+                       N_("show number of added and deleted lines in decimal notation")),
                OPT_BOOLEAN(0, "summary", &summary,
                        N_("instead of applying the patch, output a summary for the input")),
                OPT_BOOLEAN(0, "check", &check,
@@ -4022,6 +4336,8 @@ int cmd_apply(int argc, const char **argv, const char *prefix_)
                        N_("apply a patch without touching the working tree")),
                OPT_BOOLEAN(0, "apply", &force_apply,
                        N_("also apply the patch (use with --stat/--summary/--check)")),
+               OPT_BOOL('3', "3way", &threeway,
+                        N_( "attempt three-way merge if a patch does not apply")),
                OPT_FILENAME(0, "build-fake-ancestor", &fake_ancestor,
                        N_("build a temporary index based on embedded index information")),
                { OPTION_CALLBACK, 'z', NULL, NULL, NULL,
@@ -4070,6 +4386,15 @@ int cmd_apply(int argc, const char **argv, const char *prefix_)
        argc = parse_options(argc, argv, prefix, builtin_apply_options,
                        apply_usage, 0);
 
+       if (apply_with_reject && threeway)
+               die("--reject and --3way cannot be used together.");
+       if (cached && threeway)
+               die("--cached and --3way cannot be used together.");
+       if (threeway) {
+               if (is_not_gitdir)
+                       die(_("--3way outside a repository"));
+               check_index = 1;
+       }
        if (apply_with_reject)
                apply = apply_verbosely = 1;
        if (!force_apply && (diffstat || numstat || summary || check || fake_ancestor))