view mercurial/dirs.c @ 25018:93e015a3d1ea

commit: add ui.allowemptycommit config option

This adds a config flag that enables a user to make empty commits.
This is useful in a number of cases.

For instance, automation that creates release branches via
bookmarks may want to make empty commits to that release bookmark so that it
can't be fast-forwarded and so it can record information about the release
bookmark's creation. This is already possible with named branches, so making it
possible for bookmarks makes sense.

Another case we've wanted it is for mirroring repositories into Mercurial. We
have automation that syncs commits into hg by running things from the command
line. The ability to produce empty commits is useful for syncing unusual commits
from other VCS's.

In general, allowing the user to create the DAG as they see fit seems useful,
and when I mentioned this in IRC more than one person piped up and said they
were already hacking around this limitation by using mq, import, and
commit-dummy-change-then-amend-the-content-away style solutions.

/*
 dirs.c - dynamic directory diddling for dirstates

 Copyright 2013 Facebook

 This software may be used and distributed according to the terms of
 the GNU General Public License, incorporated herein by reference.
*/

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "util.h"

/*
 * This is a multiset of directory names, built from the files that
 * appear in a dirstate or manifest.
 *
 * A few implementation notes:
 *
 * We modify Python integers for refcounting, but those integers are
 * never visible to Python code.
 *
 * We mutate strings in-place, but leave them immutable once they can
 * be seen by Python code.
 */
typedef struct {
	PyObject_HEAD
	PyObject *dict;
} dirsObject;

static inline Py_ssize_t _finddir(PyObject *path, Py_ssize_t pos)
{
	const char *s = PyString_AS_STRING(path);

	while (pos != -1) {
		if (s[pos] == '/')
			break;
		pos -= 1;
	}

	return pos;
}

static int _addpath(PyObject *dirs, PyObject *path)
{
	const char *cpath = PyString_AS_STRING(path);
	Py_ssize_t pos = PyString_GET_SIZE(path);
	PyObject *key = NULL;
	int ret = -1;

	while ((pos = _finddir(path, pos - 1)) != -1) {
		PyObject *val;

		/* It's likely that every prefix already has an entry
		   in our dict. Try to avoid allocating and
		   deallocating a string for each prefix we check. */
		if (key != NULL)
			((PyStringObject *)key)->ob_shash = -1;
		else {
			/* Force Python to not reuse a small shared string. */
			key = PyString_FromStringAndSize(cpath,
							 pos < 2 ? 2 : pos);
			if (key == NULL)
				goto bail;
		}
		PyString_GET_SIZE(key) = pos;
		PyString_AS_STRING(key)[pos] = '\0';

		val = PyDict_GetItem(dirs, key);
		if (val != NULL) {
			PyInt_AS_LONG(val) += 1;
			break;
		}

		/* Force Python to not reuse a small shared int. */
		val = PyInt_FromLong(0x1eadbeef);

		if (val == NULL)
			goto bail;

		PyInt_AS_LONG(val) = 1;
		ret = PyDict_SetItem(dirs, key, val);
		Py_DECREF(val);
		if (ret == -1)
			goto bail;
		Py_CLEAR(key);
	}
	ret = 0;

bail:
	Py_XDECREF(key);

	return ret;
}

static int _delpath(PyObject *dirs, PyObject *path)
{
	Py_ssize_t pos = PyString_GET_SIZE(path);
	PyObject *key = NULL;
	int ret = -1;

	while ((pos = _finddir(path, pos - 1)) != -1) {
		PyObject *val;

		key = PyString_FromStringAndSize(PyString_AS_STRING(path), pos);

		if (key == NULL)
			goto bail;

		val = PyDict_GetItem(dirs, key);
		if (val == NULL) {
			PyErr_SetString(PyExc_ValueError,
					"expected a value, found none");
			goto bail;
		}

		if (--PyInt_AS_LONG(val) <= 0) {
			if (PyDict_DelItem(dirs, key) == -1)
				goto bail;
		} else
			break;
		Py_CLEAR(key);
	}
	ret = 0;

bail:
	Py_XDECREF(key);

	return ret;
}

static int dirs_fromdict(PyObject *dirs, PyObject *source, char skipchar)
{
	PyObject *key, *value;
	Py_ssize_t pos = 0;

	while (PyDict_Next(source, &pos, &key, &value)) {
		if (!PyString_Check(key)) {
			PyErr_SetString(PyExc_TypeError, "expected string key");
			return -1;
		}
		if (skipchar) {
			if (!dirstate_tuple_check(value)) {
				PyErr_SetString(PyExc_TypeError,
						"expected a dirstate tuple");
				return -1;
			}
			if (((dirstateTupleObject *)value)->state == skipchar)
				continue;
		}

		if (_addpath(dirs, key) == -1)
			return -1;
	}

	return 0;
}

static int dirs_fromiter(PyObject *dirs, PyObject *source)
{
	PyObject *iter, *item = NULL;
	int ret;

	iter = PyObject_GetIter(source);
	if (iter == NULL)
		return -1;

	while ((item = PyIter_Next(iter)) != NULL) {
		if (!PyString_Check(item)) {
			PyErr_SetString(PyExc_TypeError, "expected string");
			break;
		}

		if (_addpath(dirs, item) == -1)
			break;
		Py_CLEAR(item);
	}

	ret = PyErr_Occurred() ? -1 : 0;
	Py_DECREF(iter);
	Py_XDECREF(item);
	return ret;
}

/*
 * Calculate a refcounted set of directory names for the files in a
 * dirstate.
 */
static int dirs_init(dirsObject *self, PyObject *args)
{
	PyObject *dirs = NULL, *source = NULL;
	char skipchar = 0;
	int ret = -1;

	self->dict = NULL;

	if (!PyArg_ParseTuple(args, "|Oc:__init__", &source, &skipchar))
		return -1;

	dirs = PyDict_New();

	if (dirs == NULL)
		return -1;

	if (source == NULL)
		ret = 0;
	else if (PyDict_Check(source))
		ret = dirs_fromdict(dirs, source, skipchar);
	else if (skipchar)
		PyErr_SetString(PyExc_ValueError,
				"skip character is only supported "
				"with a dict source");
	else
		ret = dirs_fromiter(dirs, source);

	if (ret == -1)
		Py_XDECREF(dirs);
	else
		self->dict = dirs;

	return ret;
}

PyObject *dirs_addpath(dirsObject *self, PyObject *args)
{
	PyObject *path;

	if (!PyArg_ParseTuple(args, "O!:addpath", &PyString_Type, &path))
		return NULL;

	if (_addpath(self->dict, path) == -1)
		return NULL;

	Py_RETURN_NONE;
}

static PyObject *dirs_delpath(dirsObject *self, PyObject *args)
{
	PyObject *path;

	if (!PyArg_ParseTuple(args, "O!:delpath", &PyString_Type, &path))
		return NULL;

	if (_delpath(self->dict, path) == -1)
		return NULL;

	Py_RETURN_NONE;
}

static int dirs_contains(dirsObject *self, PyObject *value)
{
	return PyString_Check(value) ? PyDict_Contains(self->dict, value) : 0;
}

static void dirs_dealloc(dirsObject *self)
{
	Py_XDECREF(self->dict);
	PyObject_Del(self);
}

static PyObject *dirs_iter(dirsObject *self)
{
	return PyObject_GetIter(self->dict);
}

static PySequenceMethods dirs_sequence_methods;

static PyMethodDef dirs_methods[] = {
	{"addpath", (PyCFunction)dirs_addpath, METH_VARARGS, "add a path"},
	{"delpath", (PyCFunction)dirs_delpath, METH_VARARGS, "remove a path"},
	{NULL} /* Sentinel */
};

static PyTypeObject dirsType = { PyObject_HEAD_INIT(NULL) };

void dirs_module_init(PyObject *mod)
{
	dirs_sequence_methods.sq_contains = (objobjproc)dirs_contains;
	dirsType.tp_name = "parsers.dirs";
	dirsType.tp_new = PyType_GenericNew;
	dirsType.tp_basicsize = sizeof(dirsObject);
	dirsType.tp_dealloc = (destructor)dirs_dealloc;
	dirsType.tp_as_sequence = &dirs_sequence_methods;
	dirsType.tp_flags = Py_TPFLAGS_DEFAULT;
	dirsType.tp_doc = "dirs";
	dirsType.tp_iter = (getiterfunc)dirs_iter;
	dirsType.tp_methods = dirs_methods;
	dirsType.tp_init = (initproc)dirs_init;

	if (PyType_Ready(&dirsType) < 0)
		return;
	Py_INCREF(&dirsType);

	PyModule_AddObject(mod, "dirs", (PyObject *)&dirsType);
}