Port blame from git.git

1 files changed, 591 insertions, 0 deletions

diff --git a/src/blame_git.c b/src/blame_git.c
new file mode 100644
index 000000000..0dae2d9c1
--- /dev/null
+++ b/src/blame_git.c
@@ -0,0 +1,591 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "blame_git.h"
+#include "commit.h"
+
+/*
+ * Locate an existing origin or create a new one.
+ */
+int get_origin(struct origin **out, struct scoreboard *sb, git_commit *commit, const char *path)
+{
+	struct blame_entry *e;
+
+	for (e = sb->ent; e; e = e->next)
+		if (e->suspect->commit == commit && !strcmp(e->suspect->path, path))
+			*out = origin_incref(e->suspect);
+	return make_origin(out, commit, path);
+}
+
+/*
+ * Given a commit and a path in it, create a new origin structure.
+ * The callers that add blame to the scoreboard should use
+ * get_origin() to obtain shared, refcounted copy instead of calling
+ * this function directly.
+ */
+int make_origin(struct origin **out, git_commit *commit, const char *path)
+{
+	int error = 0;
+	struct origin *o;
+	o = git__calloc(1, sizeof(*o) + strlen(path) + 1);
+	GITERR_CHECK_ALLOC(o);
+	o->commit = commit;
+	o->refcnt = 1;
+	strcpy(o->path, path);
+
+	if (!(error = git_object_lookup_bypath((git_object**)&o->blob, (git_object*)commit,
+			path, GIT_OBJ_BLOB)))
+		*out = o;
+	else
+		origin_decref(o);
+	return error;
+}
+
+struct blame_chunk_cb_data {
+	struct scoreboard *sb;
+	struct origin *target;
+	struct origin *parent;
+	long plno;
+	long tlno;
+};
+
+static bool same_suspect(struct origin *a, struct origin *b)
+{
+	if (a == b)
+		return true;
+	if (git_oid_cmp(git_commit_id(a->commit), git_commit_id(b->commit)))
+		return false;
+	return 0 == strcmp(a->path, b->path);
+}
+
+/* Find the line number of the last line the target is suspected for */
+static int find_last_in_target(struct scoreboard *sb, struct origin *target)
+{
+	struct blame_entry *e;
+	int last_in_target = -1;
+
+	for (e=sb->ent; e; e=e->next) {
+		if (e->guilty || !same_suspect(e->suspect, target))
+			continue;
+		if (last_in_target < e->s_lno + e->num_lines)
+			last_in_target = e->s_lno + e->num_lines;
+	}
+	return last_in_target;
+}
+
+/*
+ * It is known that lines between tlno to same came from parent, and e
+ * has an overlap with that range.  it also is known that parent's
+ * line plno corresponds to e's line tlno.
+ *
+ *                <---- e ----->
+ *                   <------>
+ *                   <------------>
+ *             <------------>
+ *             <------------------>
+ *
+ * Split e into potentially three parts; before this chunk, the chunk
+ * to be blamed for the parent, and after that portion.
+ */
+static void split_overlap(struct blame_entry *split, struct blame_entry *e,
+		int tlno, int plno, int same, struct origin *parent)
+{
+	int chunk_end_lno;
+
+	if (e->s_lno < tlno) {
+		/* there is a pre-chunk part not blamed on the parent */
+		split[0].suspect = origin_incref(e->suspect);
+		split[0].lno = e->lno;
+		split[0].s_lno = e->s_lno;
+		split[0].num_lines = tlno - e->s_lno;
+		split[1].lno = e->lno + tlno - e->s_lno;
+		split[1].s_lno = plno;
+	} else {
+		split[1].lno = e->lno;
+		split[1].s_lno = plno + (e->s_lno - tlno);
+	}
+
+	if (same < e->s_lno + e->num_lines) {
+		/* there is a post-chunk part not blamed on parent */
+		split[2].suspect = origin_incref(e->suspect);
+		split[2].lno = e->lno + (same - e->s_lno);
+		split[2].s_lno = e->s_lno + (same - e->s_lno);
+		split[2].num_lines = e->s_lno + e->num_lines - same;
+		chunk_end_lno = split[2].lno;
+	} else {
+		chunk_end_lno = e->lno + e->num_lines;
+	}
+	split[1].num_lines = chunk_end_lno - split[1].lno;
+
+	/*
+	 * if it turns out there is nothing to blame the parent for, forget about
+	 * the splitting. !split[1].suspect signals this.
+	 */
+	if (split[1].num_lines < 1)
+		return;
+	split[1].suspect = origin_incref(parent);
+}
+
+/*
+ * Link in a new blame entry to the scoreboard. Entries that cover the same
+ * line range have been removed from the scoreboard previously.
+ */
+static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
+{
+	struct blame_entry *ent, *prev = NULL;
+
+	origin_incref(e->suspect);
+
+	for (ent = sb->ent; ent && ent->lno < e->lno; ent = ent->next)
+		prev = ent;
+
+	/* prev, if not NULL, is the last one that is below e */
+	e->prev = prev;
+	if (prev) {
+		e->next = prev->next;
+		prev->next = e;
+	} else {
+		e->next = sb->ent;
+		sb->ent = e;
+	}
+	if (e->next)
+		e->next->prev = e;
+}
+
+/*
+ * src typically is on-stack; we want to copy the information in it to
+ * a malloced blame_entry that is already on the linked list of the scoreboard.
+ * The origin of dst loses a refcnt while the origin of src gains one.
+ */
+static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
+{
+	struct blame_entry *p, *n;
+
+	p = dst->prev;
+	n = dst->next;
+	origin_incref(src->suspect);
+	origin_decref(dst->suspect);
+	memcpy(dst, src, sizeof(*src));
+	dst->prev = p;
+	dst->next = n;
+	dst->score = 0;
+}
+
+/*
+ * split_overlap() divided an existing blame e into up to three parts in split.
+ * Adjust the linked list of blames in the scoreboard to reflect the split.
+ */
+static void split_blame(struct scoreboard *sb, struct blame_entry *split, struct blame_entry *e)
+{
+	struct blame_entry *new_entry;
+
+	if (split[0].suspect && split[2].suspect) {
+		/* The first part (reuse storage for the existing entry e */
+		dup_entry(e, &split[0]);
+
+		/* The last part -- me */
+		new_entry = git__malloc(sizeof(*new_entry));
+		memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
+		add_blame_entry(sb, new_entry);
+
+		/* ... and the middle part -- parent */
+		new_entry = git__malloc(sizeof(*new_entry));
+		memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
+		add_blame_entry(sb, new_entry);
+	} else if (!split[0].suspect && !split[2].suspect) {
+		/*
+		 * The parent covers the entire area; reuse storage for e and replace it
+		 * with the parent
+		 */
+		dup_entry(e, &split[1]);
+	} else if (split[0].suspect) {
+		/* me and then parent */
+		dup_entry(e, &split[0]);
+		new_entry = git__malloc(sizeof(*new_entry));
+		memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
+		add_blame_entry(sb, new_entry);
+	} else {
+		/* parent and then me */
+		dup_entry(e, &split[1]);
+		new_entry = git__malloc(sizeof(*new_entry));
+		memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
+		add_blame_entry(sb, new_entry);
+	}
+}
+
+/* 
+ * After splitting the blame, the origins used by the on-stack blame_entry
+ * should lose one refcnt each.
+ */
+static void decref_split(struct blame_entry *split)
+{
+	int i;
+	for (i=0; i<3; i++)
+		origin_decref(split[i].suspect);
+}
+
+/*
+ * Helper for blame_chunk(). blame_entry e is known to overlap with the patch
+ * hunk; split it and pass blame to the parent.
+ */
+static void blame_overlap(struct scoreboard *sb, struct blame_entry *e, int tlno, int plno, int same, struct origin *parent)
+{
+	struct blame_entry split[3] = {{0}};
+
+	split_overlap(split, e, tlno, plno, same, parent);
+	if (split[1].suspect)
+		split_blame(sb, split, e);
+	decref_split(split);
+}
+
+/*
+ * Process one hunk from the patch between the current suspect for blame_entry
+ * e and its parent. Find and split the overlap, and pass blame to the
+ * overlapping part to the parent.
+ */
+static void blame_chunk(struct scoreboard *sb, int tlno, int plno, int same, struct origin *target, struct origin *parent)
+{
+	struct blame_entry *e;
+
+	for (e = sb->ent; e; e = e->next) {
+		if (e->guilty || !same_suspect(e->suspect, target))
+			continue;
+		if (same <= e->s_lno)
+			continue;
+		if (tlno < e->s_lno + e->num_lines) {
+			blame_overlap(sb, e, tlno, plno, same, parent);
+		}
+	}
+}
+
+static void blame_chunk_cb(long start_a, long count_a, long start_b, long count_b, void *data)
+{
+	struct blame_chunk_cb_data *d = data;
+	blame_chunk(d->sb, d->tlno, d->plno, start_b, d->target, d->parent);
+	d->plno = start_a + count_a;
+	d->tlno = start_b + count_b;
+}
+
+static int my_emit_func(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb, xdemitconf_t const *xecfg)
+{
+	xdchange_t *xch = xscr;
+	GIT_UNUSED(xe);
+	GIT_UNUSED(xecfg);
+	while (xch) {
+		blame_chunk_cb(xch->i1, xch->chg1, xch->i2, xch->chg2, ecb->priv);
+		xch = xch->next;
+	}
+	return 0;
+}
+
+static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
+{
+	const int blk = 1024;
+	long trimmed = 0, recovered = 0;
+	char *ap = a->ptr + a->size;
+	char *bp = b->ptr + b->size;
+	long smaller = (a->size < b->size) ? a->size : b->size;
+
+	if (ctx)
+		return;
+
+	while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
+		trimmed += blk;
+		ap -= blk;
+		bp -= blk;
+	}
+
+	while (recovered < trimmed)
+		if (ap[recovered++] == '\n')
+			break;
+	a->size -= trimmed - recovered;
+	b->size -= trimmed - recovered;
+}
+
+static int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
+{
+	mmfile_t a = *mf1;
+	mmfile_t b = *mf2;
+
+	trim_common_tail(&a, &b, xecfg->ctxlen);
+
+	return xdl_diff(&a, &b, xpp, xecfg, xecb);
+}
+
+
+static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b, void *cb_data)
+{
+	xpparam_t xpp = {0};
+	xdemitconf_t xecfg = {0};
+	xdemitcb_t ecb = {0};
+
+	xecfg.emit_func = (void(*)(void))my_emit_func;
+	ecb.priv = cb_data;
+	return xdi_diff(file_a, file_b, &xpp, &xecfg, &ecb);
+}
+
+static void fill_origin_blob(struct origin *o, mmfile_t *file)
+{
+	memset(file, 0, sizeof(*file));
+	if (o->blob) {
+		file->ptr = (char*)git_blob_rawcontent(o->blob);
+		file->size = (size_t)git_blob_rawsize(o->blob);
+	}
+}
+
+static int pass_blame_to_parent(struct scoreboard *sb,
+				struct origin *target,
+				struct origin *parent)
+{
+	int last_in_target;
+	mmfile_t file_p, file_o;
+	struct blame_chunk_cb_data d = { sb, target, parent, 0, 0 };
+
+	last_in_target = find_last_in_target(sb, target);
+	if (last_in_target < 0)
+		return 1; /* nothing remains for this target */
+
+	fill_origin_blob(parent, &file_p);
+	fill_origin_blob(target, &file_o);
+
+	diff_hunks(&file_p, &file_o, &d);
+	/* The reset (i.e. anything after tlno) are the same as the parent */
+	blame_chunk(sb, d.tlno, d.plno, last_in_target, target, parent);
+
+	return 0;
+}
+
+static int paths_on_dup(void **old, void *new)
+{
+	GIT_UNUSED(old);
+	git__free(new);
+	return -1;
+}
+static struct origin* find_origin(struct scoreboard *sb, git_commit *parent,
+		struct origin *origin)
+{
+	struct origin *porigin = NULL;
+	git_diff_list *difflist = NULL;
+	git_diff_options diffopts = GIT_DIFF_OPTIONS_INIT;
+	git_tree *otree=NULL, *ptree=NULL;
+
+	/* Get the trees from this commit and its parent */
+	// TODO: check errors
+	git_commit_tree(&otree, origin->commit);
+	git_commit_tree(&ptree, parent);
+
+	/* Configure the diff */
+	diffopts.context_lines = 0;
+	diffopts.flags = GIT_DIFF_SKIP_BINARY_CHECK;
+
+	/* Check to see if files we're interested have changed */
+	diffopts.pathspec.count = sb->blame->paths.length;
+	diffopts.pathspec.strings = (char**)sb->blame->paths.contents;
+	// TODO: check error
+	git_diff_tree_to_tree(&difflist, sb->blame->repository, ptree, otree, &diffopts);
+
+	if (!git_diff_num_deltas(difflist)) {
+		/* No changes; copy data */
+		// TODO: check error
+		get_origin(&porigin, sb, parent, origin->path);
+	} else {
+		git_diff_find_options findopts = GIT_DIFF_FIND_OPTIONS_INIT;
+		int i;
+
+		/* Generate a full diff between the two trees */
+		git_diff_list_free(difflist);
+		diffopts.pathspec.count = 0;
+		// TODO: check error
+		git_diff_tree_to_tree(&difflist, sb->blame->repository, ptree, otree, &diffopts);
+
+		/* Let diff find renames */
+		findopts.flags = GIT_DIFF_FIND_RENAMES;
+		// TODO: check error
+		git_diff_find_similar(difflist, &findopts);
+
+		/* Find one that matches */
+		for (i=0; i<(int)git_diff_num_deltas(difflist); i++) {
+			const git_diff_delta *delta;
+			git_diff_get_patch(NULL, &delta, difflist, i);
+			if (git_vector_bsearch(NULL, &sb->blame->paths, delta->new_file.path) != 0)
+				continue;
+
+			git_vector_insert_sorted(&sb->blame->paths, (void*)git__strdup(delta->old_file.path), paths_on_dup);
+			// TODO: check error
+			make_origin(&porigin, parent, delta->old_file.path);
+		}
+	}
+
+	git_diff_list_free(difflist);
+	git_tree_free(otree);
+	git_tree_free(ptree);
+	return porigin;
+
+}
+
+/*
+ * The blobs of origin and porigin exactly match, so everything origin is
+ * suspected for can be blamed on the parent.
+ */
+static void pass_whole_blame(struct scoreboard *sb,
+		struct origin *origin, struct origin *porigin)
+{
+	struct blame_entry *e;
+
+	if (!porigin->blob)
+		git_object_lookup((git_object**)&porigin->blob, sb->blame->repository, git_blob_id(origin->blob),
+				GIT_OBJ_BLOB);
+	for (e=sb->ent; e; e=e->next) {
+		if (!same_suspect(e->suspect, origin))
+			continue;
+		origin_incref(porigin);
+		origin_decref(e->suspect);
+		e->suspect = porigin;
+	}
+}
+
+static void pass_blame(struct scoreboard *sb, struct origin *origin, uint32_t opt)
+{
+	git_commit *commit = origin->commit;
+	int i, num_sg;
+	struct origin *sg_buf[16];
+	struct origin *porigin, **sg_origin = sg_buf;
+
+	GIT_UNUSED(opt);
+
+	num_sg = git_commit_parentcount(commit);
+	if (!num_sg)
+		goto finish;
+	else if (num_sg < (int)ARRAY_SIZE(sg_buf))
+		memset(sg_buf, 0, sizeof(sg_buf));
+	else
+		sg_origin = git__calloc(num_sg, sizeof(*sg_origin));
+
+	for (i=0; i<num_sg; i++) {
+		git_commit *p;
+		int j, same;
+
+		if (sg_origin[i])
+			continue;
+
+		// TODO: check error
+		git_commit_parent(&p, origin->commit, i);
+		porigin = find_origin(sb, p, origin);
+
+		if (!porigin)
+			continue;
+		if (porigin->blob && origin->blob &&
+		    !git_oid_cmp(git_blob_id(porigin->blob), git_blob_id(origin->blob))) {
+			pass_whole_blame(sb, origin, porigin);
+			origin_decref(porigin);
+			goto finish;
+		}
+		for (j = same = 0; j<i; j++)
+			if (sg_origin[j] &&
+				 !git_oid_cmp(git_blob_id(sg_origin[j]->blob), git_blob_id(porigin->blob))) {
+				same = 1;
+				break;
+			}
+		if (!same)
+			sg_origin[i] = porigin;
+		else
+			origin_decref(porigin);
+	}
+
+	for (i=0; i<num_sg; i++) {
+		struct origin *porigin = sg_origin[i];
+		if (!porigin)
+			continue;
+		if (!origin->previous) {
+			origin_incref(porigin);
+			origin->previous = porigin;
+		}
+		if (pass_blame_to_parent(sb, origin, porigin))
+			goto finish;
+	}
+
+	/* TODO: optionally find moves in parents' files */
+
+	/* TODO: optionally find copies in parents' files */
+
+finish:
+	for (i=0; i<num_sg; i++)
+		if (sg_origin[i])
+			origin_decref(sg_origin[i]);
+	if (sg_origin != sg_buf)
+		git__free(sg_origin);
+	return;
+}
+
+/*
+ * Origin is refcounted and usually we keep the blob contents to be
+ * reused.
+ */
+struct origin *origin_incref(struct origin *o)
+{
+	if (o)
+		o->refcnt++;
+	return o;
+}
+
+void origin_decref(struct origin *o)
+{
+	if (o && --o->refcnt <= 0) {
+		if (o->previous)
+			origin_decref(o->previous);
+		git_blob_free(o->blob);
+		git_commit_free(o->commit);
+		git__free(o);
+	}
+}
+
+void assign_blame(struct scoreboard *sb, uint32_t opt)
+{
+	while (true) {
+		struct blame_entry *ent;
+		struct origin *suspect = NULL;
+
+		/* Find a suspect to break down */
+		for (ent = sb->ent; !suspect && ent; ent = ent->next)
+			if (!ent->guilty)
+				suspect = ent->suspect;
+		if (!suspect)
+			return; /* all done */
+
+		/* We'll use this suspect later in the loop, so hold on to it for now. */
+		origin_incref(suspect);
+		pass_blame(sb, suspect, opt);
+
+		/* Take responsibility for the remaining entries */
+		for (ent = sb->ent; ent; ent = ent->next)
+			if (same_suspect(ent->suspect, suspect))
+				ent->guilty = 1;
+		origin_decref(suspect);
+	}
+}
+
+void coalesce(struct scoreboard *sb)
+{
+	struct blame_entry *ent, *next;
+
+	for (ent=sb->ent; ent && (next = ent->next); ent = next) {
+		if (same_suspect(ent->suspect, next->suspect) &&
+		    ent->guilty == next->guilty &&
+		    ent->s_lno + ent->num_lines == next->s_lno)
+		{
+			ent->num_lines += next->num_lines;
+			ent->next = next->next;
+			if (ent->next)
+				ent->next->prev = ent;
+			origin_decref(next->suspect);
+			git__free(next);
+			ent->score = 0;
+			next = ent; /* again */
+		}
+	}
+}
+