[PATCH v2 1/5] revert: libify pick

[PATCH v2 1/5] revert: libify pick

[Christian Couder]

From: Stephan Beyer <s-beyer@gmx.net>

This commit is made of code from the sequencer GSoC project:

git://repo.or.cz/git/sbeyer.git

(commit e7b8dab0c2a73ade92017a52bb1405ea1534ef20)

The goal of this commit is to abstract out pick functionnality
into a new pick() function made of code from "builtin-revert.c".

The new pick() function is in a new "pick.c" file with an
associated "pick.h".

"pick.h" and "pick.c" are strictly the same as on the sequencer repo,
but a few changes were needed on "builtin-revert.c" to keep it up to
date with changes on git.git.

Mentored-by: Daniel Barkalow <barkalow@iabervon.org>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 Makefile         |    2 +
 builtin-revert.c |  272 +++++++++---------------------------------------------
 pick.c           |  229 +++++++++++++++++++++++++++++++++++++++++++++
 pick.h           |   13 +++
 4 files changed, 288 insertions(+), 228 deletions(-)
 create mode 100644 pick.c
 create mode 100644 pick.h

diff --git a/Makefile b/Makefile
index 6b39d56..139a7b7 100644
--- a/Makefile
+++ b/Makefile
@@ -438,6 +438,7 @@ LIB_H += pack-refs.h
 LIB_H += pack-revindex.h
 LIB_H += parse-options.h
 LIB_H += patch-ids.h
+LIB_H += pick.h
 LIB_H += pkt-line.h
 LIB_H += progress.h
 LIB_H += quote.h
@@ -526,6 +527,7 @@ LIB_OBJS += parse-options.o
 LIB_OBJS += patch-delta.o
 LIB_OBJS += patch-ids.o
 LIB_OBJS += path.o
+LIB_OBJS += pick.o
 LIB_OBJS += pkt-line.o
 LIB_OBJS += preload-index.o
 LIB_OBJS += pretty.o
diff --git a/builtin-revert.c b/builtin-revert.c
index 151aa6a..6dd29a3 100644
--- a/builtin-revert.c
+++ b/builtin-revert.c
@@ -1,18 +1,14 @@
 #include "cache.h"
 #include "builtin.h"
-#include "object.h"
 #include "commit.h"
 #include "tag.h"
-#include "wt-status.h"
-#include "run-command.h"
 #include "exec_cmd.h"
 #include "utf8.h"
 #include "parse-options.h"
-#include "cache-tree.h"
 #include "diff.h"
 #include "revision.h"
 #include "rerere.h"
-#include "merge-recursive.h"
+#include "pick.h"
 
 /*
  * This implements the builtins revert and cherry-pick.
@@ -35,25 +31,23 @@ static const char * const cherry_pick_usage[] = {
 	NULL
 };
 
-static int edit, no_replay, no_commit, mainline, signoff;
-static enum { REVERT, CHERRY_PICK } action;
+static int edit, no_commit, mainline, signoff;
+static int flags;
 static struct commit *commit;
 
-static const char *me;
-
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
 static void parse_args(int argc, const char **argv)
 {
 	const char * const * usage_str =
-		action == REVERT ?  revert_usage : cherry_pick_usage;
+		flags & PICK_REVERSE ? revert_usage : cherry_pick_usage;
 	unsigned char sha1[20];
 	const char *arg;
 	int noop;
 	struct option options[] = {
 		OPT_BOOLEAN('n', "no-commit", &no_commit, "don't automatically commit"),
 		OPT_BOOLEAN('e', "edit", &edit, "edit the commit message"),
-		OPT_BOOLEAN('x', NULL, &no_replay, "append commit name when cherry-picking"),
+		OPT_BIT('x', NULL, &flags, "append commit name when cherry-picking", PICK_ADD_NOTE),
 		OPT_BOOLEAN('r', NULL, &noop, "no-op (backward compatibility)"),
 		OPT_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by:"),
 		OPT_INTEGER('m', "mainline", &mainline, "parent number"),
@@ -77,42 +71,12 @@ static void parse_args(int argc, const char **argv)
 		die ("'%s' does not point to a commit", arg);
 }
 
-static char *get_oneline(const char *message)
-{
-	char *result;
-	const char *p = message, *abbrev, *eol;
-	int abbrev_len, oneline_len;
-
-	if (!p)
-		die ("Could not read commit message of %s",
-				sha1_to_hex(commit->object.sha1));
-	while (*p && (*p != '\n' || p[1] != '\n'))
-		p++;
-
-	if (*p) {
-		p += 2;
-		for (eol = p + 1; *eol && *eol != '\n'; eol++)
-			; /* do nothing */
-	} else
-		eol = p;
-	abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
-	abbrev_len = strlen(abbrev);
-	oneline_len = eol - p;
-	result = xmalloc(abbrev_len + 5 + oneline_len);
-	memcpy(result, abbrev, abbrev_len);
-	memcpy(result + abbrev_len, "... ", 4);
-	memcpy(result + abbrev_len + 4, p, oneline_len);
-	result[abbrev_len + 4 + oneline_len] = '\0';
-	return result;
-}
-
 static char *get_encoding(const char *message)
 {
 	const char *p = message, *eol;
 
 	if (!p)
-		die ("Could not read commit message of %s",
-				sha1_to_hex(commit->object.sha1));
+		return NULL;
 	while (*p && *p != '\n') {
 		for (eol = p + 1; *eol && *eol != '\n'; eol++)
 			; /* do nothing */
@@ -128,30 +92,6 @@ static char *get_encoding(const char *message)
 	return NULL;
 }
 
-static struct lock_file msg_file;
-static int msg_fd;
-
-static void add_to_msg(const char *string)
-{
-	int len = strlen(string);
-	if (write_in_full(msg_fd, string, len) < 0)
-		die_errno ("Could not write to MERGE_MSG");
-}
-
-static void add_message_to_msg(const char *message)
-{
-	const char *p = message;
-	while (*p && (*p != '\n' || p[1] != '\n'))
-		p++;
-
-	if (!*p)
-		add_to_msg(sha1_to_hex(commit->object.sha1));
-
-	p += 2;
-	add_to_msg(p);
-	return;
-}
-
 static void set_author_ident_env(const char *message)
 {
 	const char *p = message;
@@ -214,7 +154,7 @@ static char *help_msg(const unsigned char *sha1)
 	       "mark the corrected paths with 'git add <paths>' "
 	       "or 'git rm <paths>' and commit the result.");
 
-	if (action == CHERRY_PICK) {
+	if (!(flags & PICK_REVERSE)) {
 		sprintf(helpbuf + strlen(helpbuf),
 			"\nWhen commiting, use the option "
 			"'-c %s' to retain authorship and message.",
@@ -223,187 +163,68 @@ static char *help_msg(const unsigned char *sha1)
 	return helpbuf;
 }
 
-static struct tree *empty_tree(void)
+static void write_message(struct strbuf *msgbuf, const char *filename)
 {
-	struct tree *tree = xcalloc(1, sizeof(struct tree));
-
-	tree->object.parsed = 1;
-	tree->object.type = OBJ_TREE;
-	pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
-	return tree;
+	struct lock_file msg_file;
+	int msg_fd;
+	msg_fd = hold_lock_file_for_update(&msg_file, filename,
+					   LOCK_DIE_ON_ERROR);
+	if (write_in_full(msg_fd, msgbuf->buf, msgbuf->len) < 0)
+		die_errno("Could not write to %s.", filename);
+	strbuf_release(msgbuf);
+	if (commit_lock_file(&msg_file) < 0)
+		die("Error wrapping up %s", filename);
 }
 
 static int revert_or_cherry_pick(int argc, const char **argv)
 {
-	unsigned char head[20];
-	struct commit *base, *next, *parent;
-	int i, index_fd, clean;
-	char *oneline, *reencoded_message = NULL;
-	const char *message, *encoding;
-	char *defmsg = git_pathdup("MERGE_MSG");
-	struct merge_options o;
-	struct tree *result, *next_tree, *base_tree, *head_tree;
-	static struct lock_file index_lock;
+	const char *me;
+	struct strbuf msgbuf;
+	char *reencoded_message = NULL;
+	const char *encoding;
+	int failed;
 
 	git_config(git_default_config, NULL);
-	me = action == REVERT ? "revert" : "cherry-pick";
+	me = flags & PICK_REVERSE ? "revert" : "cherry-pick";
 	setenv(GIT_REFLOG_ACTION, me, 0);
 	parse_args(argc, argv);
 
-	/* this is copied from the shell script, but it's never triggered... */
-	if (action == REVERT && !no_replay)
-		die("revert is incompatible with replay");
-
 	if (read_cache() < 0)
 		die("git %s: failed to read the index", me);
-	if (no_commit) {
-		/*
-		 * We do not intend to commit immediately.  We just want to
-		 * merge the differences in, so let's compute the tree
-		 * that represents the "current" state for merge-recursive
-		 * to work on.
-		 */
-		if (write_cache_as_tree(head, 0, NULL))
-			die ("Your index file is unmerged.");
-	} else {
-		if (get_sha1("HEAD", head))
-			die ("You do not have a valid HEAD");
-		if (index_differs_from("HEAD", 0))
-			die ("Dirty index: cannot %s", me);
-	}
-	discard_cache();
-
-	index_fd = hold_locked_index(&index_lock, 1);
+	if (!no_commit && index_differs_from("HEAD", 0))
+		die ("Dirty index: cannot %s", me);
 
-	if (!commit->parents) {
-		if (action == REVERT)
-			die ("Cannot revert a root commit");
-		parent = NULL;
-	}
-	else if (commit->parents->next) {
-		/* Reverting or cherry-picking a merge commit */
-		int cnt;
-		struct commit_list *p;
-
-		if (!mainline)
-			die("Commit %s is a merge but no -m option was given.",
-			    sha1_to_hex(commit->object.sha1));
-
-		for (cnt = 1, p = commit->parents;
-		     cnt != mainline && p;
-		     cnt++)
-			p = p->next;
-		if (cnt != mainline || !p)
-			die("Commit %s does not have parent %d",
-			    sha1_to_hex(commit->object.sha1), mainline);
-		parent = p->item;
-	} else if (0 < mainline)
-		die("Mainline was specified but commit %s is not a merge.",
-		    sha1_to_hex(commit->object.sha1));
-	else
-		parent = commit->parents->item;
-
-	if (!(message = commit->buffer))
-		die ("Cannot get commit message for %s",
+	if (!commit->buffer)
+		return error("Cannot get commit message for %s",
 				sha1_to_hex(commit->object.sha1));
-
-	if (parent && parse_commit(parent) < 0)
-		die("%s: cannot parse parent commit %s",
-		    me, sha1_to_hex(parent->object.sha1));
-
-	/*
-	 * "commit" is an existing commit.  We would want to apply
-	 * the difference it introduces since its first parent "prev"
-	 * on top of the current HEAD if we are cherry-pick.  Or the
-	 * reverse of it if we are revert.
-	 */
-
-	msg_fd = hold_lock_file_for_update(&msg_file, defmsg,
-					   LOCK_DIE_ON_ERROR);
-
-	encoding = get_encoding(message);
+	encoding = get_encoding(commit->buffer);
 	if (!encoding)
 		encoding = "UTF-8";
 	if (!git_commit_encoding)
 		git_commit_encoding = "UTF-8";
-	if ((reencoded_message = reencode_string(message,
+	if ((reencoded_message = reencode_string(commit->buffer,
 					git_commit_encoding, encoding)))
-		message = reencoded_message;
-
-	oneline = get_oneline(message);
-
-	if (action == REVERT) {
-		char *oneline_body = strchr(oneline, ' ');
+		commit->buffer = reencoded_message;
 
-		base = commit;
-		next = parent;
-		add_to_msg("Revert \"");
-		add_to_msg(oneline_body + 1);
-		add_to_msg("\"\n\nThis reverts commit ");
-		add_to_msg(sha1_to_hex(commit->object.sha1));
-
-		if (commit->parents->next) {
-			add_to_msg(", reversing\nchanges made to ");
-			add_to_msg(sha1_to_hex(parent->object.sha1));
-		}
-		add_to_msg(".\n");
-	} else {
-		base = parent;
-		next = commit;
-		set_author_ident_env(message);
-		add_message_to_msg(message);
-		if (no_replay) {
-			add_to_msg("(cherry picked from commit ");
-			add_to_msg(sha1_to_hex(commit->object.sha1));
-			add_to_msg(")\n");
-		}
-	}
-
-	read_cache();
-	init_merge_options(&o);
-	o.branch1 = "HEAD";
-	o.branch2 = oneline;
-
-	head_tree = parse_tree_indirect(head);
-	next_tree = next ? next->tree : empty_tree();
-	base_tree = base ? base->tree : empty_tree();
-
-	clean = merge_trees(&o,
-			    head_tree,
-			    next_tree, base_tree, &result);
-
-	if (active_cache_changed &&
-	    (write_cache(index_fd, active_cache, active_nr) ||
-	     commit_locked_index(&index_lock)))
-		die("%s: Unable to write new index file", me);
-	rollback_lock_file(&index_lock);
-
-	if (!clean) {
-		add_to_msg("\nConflicts:\n\n");
-		for (i = 0; i < active_nr;) {
-			struct cache_entry *ce = active_cache[i++];
-			if (ce_stage(ce)) {
-				add_to_msg("\t");
-				add_to_msg(ce->name);
-				add_to_msg("\n");
-				while (i < active_nr && !strcmp(ce->name,
-						active_cache[i]->name))
-					i++;
-			}
-		}
-		if (commit_lock_file(&msg_file) < 0)
-			die ("Error wrapping up %s", defmsg);
+	failed = pick(commit, mainline, flags, &msgbuf);
+	if (failed < 0) {
+		exit(1);
+	} else if (failed > 0) {
 		fprintf(stderr, "Automatic %s failed.%s\n",
 			me, help_msg(commit->object.sha1));
+		write_message(&msgbuf, git_path("MERGE_MSG"));
 		rerere();
 		exit(1);
 	}
-	if (commit_lock_file(&msg_file) < 0)
-		die ("Error wrapping up %s", defmsg);
+	if (!(flags & PICK_REVERSE))
+		set_author_ident_env(commit->buffer);
+	free(reencoded_message);
+
 	fprintf(stderr, "Finished one %s.\n", me);
 
+	write_message(&msgbuf, git_path("MERGE_MSG"));
+
 	/*
-	 *
 	 * If we are cherry-pick, and if the merge did not result in
 	 * hand-editing, we will hit this commit and inherit the original
 	 * author date and name.
@@ -421,14 +242,11 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 			args[i++] = "-s";
 		if (!edit) {
 			args[i++] = "-F";
-			args[i++] = defmsg;
+			args[i++] = git_path("MERGE_MSG");
 		}
 		args[i] = NULL;
 		return execv_git_cmd(args);
 	}
-	free(reencoded_message);
-	free(defmsg);
-
 	return 0;
 }
 
@@ -436,14 +254,12 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
 {
 	if (isatty(0))
 		edit = 1;
-	no_replay = 1;
-	action = REVERT;
+	flags = PICK_REVERSE | PICK_ADD_NOTE;
 	return revert_or_cherry_pick(argc, argv);
 }
 
 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 {
-	no_replay = 0;
-	action = CHERRY_PICK;
+	flags = 0;
 	return revert_or_cherry_pick(argc, argv);
 }
diff --git a/pick.c b/pick.c
new file mode 100644
index 0000000..77c7169
--- /dev/null
+++ b/pick.c
@@ -0,0 +1,229 @@
+#include "cache.h"
+#include "commit.h"
+#include "run-command.h"
+#include "cache-tree.h"
+#include "pick.h"
+#include "merge-recursive.h"
+
+static struct commit *commit;
+
+static char *get_oneline(const char *message)
+{
+	char *result;
+	const char *p = message, *abbrev, *eol;
+	int abbrev_len, oneline_len;
+
+	if (!p)
+		return NULL;
+	while (*p && (*p != '\n' || p[1] != '\n'))
+		p++;
+
+	if (*p) {
+		p += 2;
+		for (eol = p + 1; *eol && *eol != '\n'; eol++)
+			; /* do nothing */
+	} else
+		eol = p;
+	abbrev = find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV);
+	abbrev_len = strlen(abbrev);
+	oneline_len = eol - p;
+	result = xmalloc(abbrev_len + 5 + oneline_len);
+	memcpy(result, abbrev, abbrev_len);
+	memcpy(result + abbrev_len, "... ", 4);
+	memcpy(result + abbrev_len + 4, p, oneline_len);
+	result[abbrev_len + 4 + oneline_len] = '\0';
+	return result;
+}
+
+static void add_message_to_msg(struct strbuf *msg, const char *message)
+{
+	const char *p = message;
+	while (*p && (*p != '\n' || p[1] != '\n'))
+		p++;
+
+	if (!*p)
+		strbuf_addstr(msg, sha1_to_hex(commit->object.sha1));
+
+	p += 2;
+	strbuf_addstr(msg, p);
+	return;
+}
+
+static struct tree *empty_tree(void)
+{
+	struct tree *tree = xcalloc(1, sizeof(struct tree));
+
+	tree->object.parsed = 1;
+	tree->object.type = OBJ_TREE;
+	pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
+	return tree;
+}
+
+/*
+ * Pick changes introduced by pick_commit into current working tree
+ * and index.
+ *
+ * Return 0 on success.
+ * Return negative value on error before picking,
+ * and a positive value after picking,
+ * and return 1 if and only if a conflict occurs but no other error.
+ */
+int pick(struct commit *pick_commit, int mainline, int flags,
+						struct strbuf *msg)
+{
+	unsigned char head[20];
+	struct commit *base, *next, *parent;
+	int i, index_fd, clean;
+	int ret = 0;
+	char *oneline;
+	const char *message;
+	struct merge_options o;
+	struct tree *result, *next_tree, *base_tree, *head_tree;
+	static struct lock_file index_lock;
+
+	strbuf_init(msg, 0);
+	commit = pick_commit;
+
+	if (flags & PICK_REVERSE) /* REVERSE implies ADD_NOTE */
+		flags |= PICK_ADD_NOTE;
+
+	/*
+	 * We do not intend to commit immediately.  We just want to
+	 * merge the differences in, so let's compute the tree
+	 * that represents the "current" state for merge-recursive
+	 * to work on.
+	 */
+	if (write_cache_as_tree(head, 0, NULL)) {
+		error("Your index file is unmerged.");
+		return -1;
+	}
+	discard_cache();
+
+	index_fd = hold_locked_index(&index_lock, 0);
+	if (index_fd < 0) {
+		error("Unable to create locked index: %s",
+						strerror(errno));
+		return -1;
+	}
+
+	if (!commit->parents) {
+		if (flags & PICK_REVERSE) {
+			error("Cannot revert a root commit");
+			return -1;
+		}
+		parent = NULL;
+	}
+	else if (commit->parents->next) {
+		/* Reverting or cherry-picking a merge commit */
+		int cnt;
+		struct commit_list *p;
+
+		if (!mainline) {
+			error("Commit %s is a merge but no mainline was given.",
+			    sha1_to_hex(commit->object.sha1));
+			return -1;
+		}
+
+		for (cnt = 1, p = commit->parents;
+		     cnt != mainline && p;
+		     cnt++)
+			p = p->next;
+		if (cnt != mainline || !p) {
+			error("Commit %s does not have parent %d",
+			    sha1_to_hex(commit->object.sha1), mainline);
+			return -1;
+		}
+		parent = p->item;
+	} else if (0 < mainline) {
+		error("Mainline was specified but commit %s is not a merge.",
+		    sha1_to_hex(commit->object.sha1));
+		return -1;
+	} else
+		parent = commit->parents->item;
+
+	if (!(message = commit->buffer)) {
+		error("Cannot get commit message for %s",
+				sha1_to_hex(commit->object.sha1));
+		return -1;
+	}
+
+	if (parent && parse_commit(parent) < 0) {
+		error("Cannot parse parent commit %s",
+		      sha1_to_hex(parent->object.sha1));
+		return -1;
+	}
+
+	oneline = get_oneline(message);
+
+	if (flags & PICK_REVERSE) {
+		char *oneline_body = strchr(oneline, ' ');
+
+		base = commit;
+		next = parent;
+		strbuf_addstr(msg, "Revert \"");
+		strbuf_addstr(msg, oneline_body + 1);
+		strbuf_addstr(msg, "\"\n\nThis reverts commit ");
+		strbuf_addstr(msg, sha1_to_hex(commit->object.sha1));
+
+		if (commit->parents->next) {
+			strbuf_addstr(msg, ", reversing\nchanges made to ");
+			strbuf_addstr(msg, sha1_to_hex(parent->object.sha1));
+		}
+		strbuf_addstr(msg, ".\n");
+	} else {
+		base = parent;
+		next = commit;
+		add_message_to_msg(msg, message);
+		if (flags & PICK_ADD_NOTE) {
+			strbuf_addstr(msg, "(cherry picked from commit ");
+			strbuf_addstr(msg, sha1_to_hex(commit->object.sha1));
+			strbuf_addstr(msg, ")\n");
+		}
+	}
+
+	read_cache();
+	init_merge_options(&o);
+	o.branch1 = "HEAD";
+	o.branch2 = oneline;
+
+	head_tree = parse_tree_indirect(head);
+	next_tree = next ? next->tree : empty_tree();
+	base_tree = base ? base->tree : empty_tree();
+
+	clean = merge_trees(&o,
+			    head_tree,
+			    next_tree, base_tree, &result);
+
+	if (active_cache_changed &&
+	    (write_cache(index_fd, active_cache, active_nr) ||
+	     commit_locked_index(&index_lock))) {
+		error("Unable to write new index file");
+		return 2;
+	}
+	rollback_lock_file(&index_lock);
+
+	if (!clean) {
+		strbuf_addstr(msg, "\nConflicts:\n\n");
+		for (i = 0; i < active_nr;) {
+			struct cache_entry *ce = active_cache[i++];
+			if (ce_stage(ce)) {
+				strbuf_addstr(msg, "\t");
+				strbuf_addstr(msg, ce->name);
+				strbuf_addstr(msg, "\n");
+				while (i < active_nr && !strcmp(ce->name,
+						active_cache[i]->name))
+					i++;
+			}
+		}
+		ret = 1;
+	}
+	free(oneline);
+
+	discard_cache();
+	if (read_cache() < 0) {
+		error("Cannot read the index");
+		return 2;
+	}
+
+	return ret;
+}
diff --git a/pick.h b/pick.h
new file mode 100644
index 0000000..7eb0d3a
--- /dev/null
+++ b/pick.h
@@ -0,0 +1,13 @@
+#ifndef PICK_H
+#define PICK_H
+
+#include "commit.h"
+
+/* Pick flags: */
+#define PICK_REVERSE   1 /* pick the reverse changes ("revert") */
+#define PICK_ADD_NOTE  2 /* add note about original commit (unless conflict) */
+/* We don't need a PICK_QUIET. This is done by
+ *	setenv("GIT_MERGE_VERBOSITY", "0", 1); */
+extern int pick(struct commit *pick_commit, int mainline, int flags, struct strbuf *msg);
+
+#endif
-- 
1.6.4.133.g8a5c8