log-tree: separate major part of diff-tree.

This separates out the part that deals with one-commit diff-tree
(and --stdin form) into a separate log-tree module.

There are two goals with this.  The more important one is to be
able to make this part available to "git log --diff", so that we
can have a native "git whatchanged" command.  Another is to
simplify the commit log generation part simpler.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 175 insertions, 0 deletions

diff --git a/log-tree.c b/log-tree.c
new file mode 100644
index 0000000000..3d404824a1
--- /dev/null
+++ b/log-tree.c
@@ -0,0 +1,175 @@
+#include "cache.h"
+#include "diff.h"
+#include "commit.h"
+#include "log-tree.h"
+
+void init_log_tree_opt(struct log_tree_opt *opt)
+{
+	memset(opt, 0, sizeof *opt);
+	opt->ignore_merges = 1;
+	opt->header_prefix = "";
+	opt->commit_format = CMIT_FMT_RAW;
+	diff_setup(&opt->diffopt);
+}
+
+int log_tree_opt_parse(struct log_tree_opt *opt, const char **av, int ac)
+{
+	const char *arg;
+	int cnt = diff_opt_parse(&opt->diffopt, av, ac);
+	if (0 < cnt)
+		return cnt;
+	arg = *av;
+	if (!strcmp(arg, "-r"))
+		opt->diffopt.recursive = 1;
+	else if (!strcmp(arg, "-t")) {
+		opt->diffopt.recursive = 1;
+		opt->diffopt.tree_in_recursive = 1;
+	}
+	else if (!strcmp(arg, "-m"))
+		opt->ignore_merges = 0;
+	else if (!strcmp(arg, "-c"))
+		opt->combine_merges = 1;
+	else if (!strcmp(arg, "--cc")) {
+		opt->dense_combined_merges = 1;
+		opt->combine_merges = 1;
+	}
+	else if (!strcmp(arg, "-v")) {
+		opt->verbose_header = 1;
+		opt->header_prefix = "diff-tree ";
+	}
+	else if (!strncmp(arg, "--pretty", 8)) {
+		opt->verbose_header = 1;
+		opt->header_prefix = "diff-tree ";
+		opt->commit_format = get_commit_format(arg+8);
+	}
+	else if (!strcmp(arg, "--root"))
+		opt->show_root_diff = 1;
+	else if (!strcmp(arg, "--no-commit-id"))
+		opt->no_commit_id = 1;
+	else if (!strcmp(arg, "--always"))
+		opt->always_show_header = 1;
+	else
+		return 0;
+	return 1;
+}
+
+int log_tree_diff_flush(struct log_tree_opt *opt)
+{
+	diffcore_std(&opt->diffopt);
+	if (diff_queue_is_empty()) {
+		int saved_fmt = opt->diffopt.output_format;
+		opt->diffopt.output_format = DIFF_FORMAT_NO_OUTPUT;
+		diff_flush(&opt->diffopt);
+		opt->diffopt.output_format = saved_fmt;
+		return 0;
+	}
+	if (opt->header) {
+		if (!opt->no_commit_id)
+			printf("%s%c", opt->header,
+			       opt->diffopt.line_termination);
+		opt->header = NULL;
+	}
+	diff_flush(&opt->diffopt);
+	return 1;
+}
+
+static int diff_root_tree(struct log_tree_opt *opt,
+			  const unsigned char *new, const char *base)
+{
+	int retval;
+	void *tree;
+	struct tree_desc empty, real;
+
+	tree = read_object_with_reference(new, tree_type, &real.size, NULL);
+	if (!tree)
+		die("unable to read root tree (%s)", sha1_to_hex(new));
+	real.buf = tree;
+
+	empty.buf = "";
+	empty.size = 0;
+	retval = diff_tree(&empty, &real, base, &opt->diffopt);
+	free(tree);
+	log_tree_diff_flush(opt);
+	return retval;
+}
+
+static const char *generate_header(struct log_tree_opt *opt,
+				   const unsigned char *commit_sha1,
+				   const unsigned char *parent_sha1,
+				   const struct commit *commit)
+{
+	static char this_header[16384];
+	int offset;
+	unsigned long len;
+	int abbrev = opt->diffopt.abbrev;
+	const char *msg = commit->buffer;
+
+	if (!opt->verbose_header)
+		return sha1_to_hex(commit_sha1);
+
+	len = strlen(msg);
+
+	offset = sprintf(this_header, "%s%s ",
+			 opt->header_prefix,
+			 diff_unique_abbrev(commit_sha1, abbrev));
+	if (commit_sha1 != parent_sha1)
+		offset += sprintf(this_header + offset, "(from %s)\n",
+				  parent_sha1
+				  ? diff_unique_abbrev(parent_sha1, abbrev)
+				  : "root");
+	else
+		offset += sprintf(this_header + offset, "(from parents)\n");
+	offset += pretty_print_commit(opt->commit_format, commit, len,
+				      this_header + offset,
+				      sizeof(this_header) - offset, abbrev);
+	if (opt->always_show_header) {
+		puts(this_header);
+		return NULL;
+	}
+	return this_header;
+}
+
+static int do_diff_combined(struct log_tree_opt *opt, struct commit *commit)
+{
+	unsigned const char *sha1 = commit->object.sha1;
+
+	opt->header = generate_header(opt, sha1, sha1, commit);
+	opt->header = diff_tree_combined_merge(sha1, opt->header,
+						opt->dense_combined_merges,
+						&opt->diffopt);
+	if (!opt->header && opt->verbose_header)
+		opt->header_prefix = "\ndiff-tree ";
+	return 0;
+}
+
+int log_tree_commit(struct log_tree_opt *opt, struct commit *commit)
+{
+	struct commit_list *parents;
+	unsigned const char *sha1 = commit->object.sha1;
+
+	/* Root commit? */
+	if (opt->show_root_diff && !commit->parents) {
+		opt->header = generate_header(opt, sha1, NULL, commit);
+		diff_root_tree(opt, sha1, "");
+	}
+
+	/* More than one parent? */
+	if (commit->parents && commit->parents->next) {
+		if (opt->ignore_merges)
+			return 0;
+		else if (opt->combine_merges)
+			return do_diff_combined(opt, commit);
+	}
+
+	for (parents = commit->parents; parents; parents = parents->next) {
+		struct commit *parent = parents->item;
+		unsigned const char *psha1 = parent->object.sha1;
+		opt->header = generate_header(opt, sha1, psha1, commit);
+		diff_tree_sha1(psha1, sha1, "", &opt->diffopt);
+		log_tree_diff_flush(opt);		
+
+		if (!opt->header && opt->verbose_header)
+			opt->header_prefix = "\ndiff-tree ";
+	}
+	return 0;
+}