Since d1c5f2a (Add git-am, applymbox replacement., 2005-10-07), git-am
supported the --3way option, and if set, would attempt to do a 3-way
merge if the initial patch application fails. Re-implement this feature
through the fall_back_threeway() function.
Signed-off-by: Paul Tan <pyokagan@xxxxxxxxx>
---
builtin/am.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 129 insertions(+), 4 deletions(-)
diff --git a/builtin/am.c b/builtin/am.c
index 71fda16..8566d22 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -19,6 +19,7 @@
#include "unpack-trees.h"
#include "branch.h"
#include "sequencer.h"
+#include "merge-recursive.h"
/**
* Returns 1 if the file is empty or does not exist, 0 otherwise.
@@ -76,6 +77,8 @@ struct am_state {
const char *resolvemsg;
int sign;
+
+ int threeway;
};
/**
@@ -659,16 +662,32 @@ static void NORETURN die_user_resolve(const struct am_state *state)
}
/*
- * Applies current patch with git-apply. Returns 0 on success, -1 otherwise.
+ * Applies current patch with git-apply. Returns 0 on success, -1 otherwise. If
+ * index_file is not NULL, the patch will be applied to that index.
*/
-static int run_apply(const struct am_state *state)
+static int run_apply(const struct am_state *state, const char *index_file)
{
struct child_process cp = CHILD_PROCESS_INIT;
cp.git_cmd = 1;
+ if (index_file)
+ argv_array_pushf(&cp.env_array, "GIT_INDEX_FILE=%s", index_file);
+
+ /*
+ * If we are allowed to fall back on 3-way merge, don't give false
+ * errors during the initial attempt.
+ */
+ if (state->threeway && !index_file) {
+ cp.no_stdout = 1;
+ cp.no_stderr = 1;
+ }
+
argv_array_push(&cp.args, "apply");
- argv_array_push(&cp.args, "--index");
+ if (index_file)
+ argv_array_push(&cp.args, "--cached");
+ else
+ argv_array_push(&cp.args, "--index");
argv_array_push(&cp.args, am_path(state, "patch"));
if (run_command(&cp))
@@ -676,8 +695,92 @@ static int run_apply(const struct am_state *state)
/* Reload index as git-apply will have modified it. */
discard_cache();
+ read_cache_from(index_file ? index_file : get_index_file());
+
+ return 0;
+}
+
+/*
+ * Builds a index that contains just the blobs needed for a 3way merge.
+ */
+static int build_fake_ancestor(const struct am_state *state, const char *index_file)
+{
+ struct child_process cp = CHILD_PROCESS_INIT;
+
+ cp.git_cmd = 1;
+ argv_array_push(&cp.args, "apply");
+ argv_array_pushf(&cp.args, "--build-fake-ancestor=%s", index_file);
+ argv_array_push(&cp.args, am_path(state, "patch"));
+
+ if (run_command(&cp))
+ return -1;
+
+ return 0;
+}
+
+/**
+ * Attempt a threeway merge, using index_path as the temporary index.
+ */
+static int fall_back_threeway(const struct am_state *state, const char *index_path)
+{
+ unsigned char orig_tree[20], his_tree[20], our_tree[20];
+ const unsigned char *bases[1] = {orig_tree};
+ struct merge_options o;
+ struct commit *result;
+
+ if (get_sha1("HEAD", our_tree) < 0)
+ hashcpy(our_tree, EMPTY_TREE_SHA1_BIN);
+
+ if (build_fake_ancestor(state, index_path))
+ return error("could not build fake ancestor");
+
+ discard_cache();
+ read_cache_from(index_path);
+
+ if (write_index_as_tree(orig_tree, &the_index, index_path, 0, NULL))
+ return error(_("Repository lacks necessary blobs to fall back on 3-way merge."));
+
+ say(state, stdout, _("Using index info to reconstruct a base tree..."));
+
+ if (!state->quiet) {
+ struct child_process cp = CHILD_PROCESS_INIT;
+ cp.git_cmd = 1;
+ argv_array_pushf(&cp.env_array, "GIT_INDEX_FILE=%s", index_path);
+ argv_array_pushl(&cp.args, "diff-index", "--cached",
+ "--diff-filter=AM", "--name-status", "HEAD", NULL);
+ run_command(&cp);
+ }
+
+ if (run_apply(state, index_path))
+ return error(_("Did you hand edit your patch?\n"
+ "It does not apply to blobs recorded in its index."));
+
+ if (write_index_as_tree(his_tree, &the_index, index_path, 0, NULL))
+ return error("could not write tree");
+
+ say(state, stdout, _("Falling back to patching base and 3-way merge..."));
+
+ discard_cache();
read_cache();
+ /*
+ * This is not so wrong. Depending on which base we picked, orig_tree
+ * may be wildly different from ours, but his_tree has the same set of
+ * wildly different changes in parts the patch did not touch, so
+ * recursive ends up canceling them, saying that we reverted all those
+ * changes.
+ */
+
+ init_merge_options(&o);
+
+ o.branch1 = "HEAD";
+ o.branch2 = firstline(state->msg.buf);
+ if (state->quiet)
+ o.verbosity = 0;
+
+ if (merge_recursive_generic(&o, our_tree, his_tree, 1, bases, &result))
+ return error(_("Failed to merge in the changes."));
+
return 0;
}
@@ -743,6 +846,7 @@ static void am_run(struct am_state *state)
while (state->cur <= state->last) {
const char *patch = am_path(state, msgnum(state));
+ int apply_status;
if (!file_exists(patch))
goto next;
@@ -755,7 +859,26 @@ static void am_run(struct am_state *state)
say(state, stdout, _("Applying: %s"), firstline(state->msg.buf));
- if (run_apply(state) < 0) {
+ apply_status = run_apply(state, NULL);
+
+ if (apply_status && state->threeway) {
+ struct strbuf sb = STRBUF_INIT;
+
+ strbuf_addstr(&sb, am_path(state, "patch-merge-index"));
+ apply_status = fall_back_threeway(state, sb.buf);
+ strbuf_release(&sb);
+
+ /*
+ * Applying the patch to an earlier tree and merging
+ * the result may have produced the same tree as ours.
+ */
+ if (!apply_status && !index_has_changes(NULL)) {
+ say(state, stdout, _("No changes -- Patch already applied."));
+ goto next;
+ }
+ }
+
+ if (apply_status) {
int value;
printf_ln(_("Patch failed at %s %s"), msgnum(state),
@@ -1007,6 +1130,8 @@ static const char * const am_usage[] = {
};
static struct option am_options[] = {
+ OPT_BOOL('3', "3way", &state.threeway,
+ N_("allow fall back on 3way merging if needed")),
OPT__QUIET(&state.quiet, N_("be quiet")),
OPT_BOOL('s', "signoff", &state.sign,
N_("add a Signed-off-by line to the commit message")),
--
2.1.4
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