Fix zombie files in merge
# HG changeset patch
# User maf46@burn.cl.cam.ac.uk
# Node ID 57667c9b93a5a743e4629d15a0e6bd76699130c3
# Parent d2994b5298fb20f87dc1d4747635b280db3c0526
Fix zombie files in merge
Keir Fraser observed the following:
> I made a small test case that illustrates the bug in merging changesets
> with 'hg remove's in them:
>
> 1. Create a repository A containing files foo & bar.
> 2. Create clone called B.
> 3. A removes file bar, and commits this removal.
> 4. B edits file foo, and commits this edit.
>
> Now, if B:
> # hg pull ../A; hg update -m; hg commit
> Then bar remains deleted.
>
> If A:
> # hg pull ../B; hg update -m; hg commit
> Then bar is resurrected!
>
> It looks as though, when you merge across a branch, any deletions in
> your own branch are forgotten.
> ...
> Fixing this is a must, as zombie files are a real pain. :-)
Keir later patched our local copy of hg as shown below, which fixes
the problem. I've also enclosed a test which captures the test Keir
outlined...
Files deleted on a branch should not automatically reappear in a merge
Patch notes:
1. The first chunk does not change behaviour, but cleans up the code
to more closely match check of 'force' in the second chunk. I
think it makes the code clearer.
2. The second chunk fixes two bugs --
i. If we choose to keep a remotely-changed locally-deleted file,
then we need to 'get' that file. If we choose to delete it
then no action need be taken (it is already deleted in the
working manifest). Without this fix, choosing to delete would
get a Python traceback.
ii. The test for whether the file was remotely-created is
insufficient. It is only true if f is not in the common
ancestor. Otherwise the file was deleted locally, and should
remain deleted. (this is the most important fix!)
Index: hg/tests/test-merge6
===================================================================
/*
mpatch.c - efficient binary patching for Mercurial
This implements a patch algorithm that's O(m + nlog n) where m is the
size of the output and n is the number of patches.
Given a list of binary patches, it unpacks each into a hunk list,
then combines the hunk lists with a treewise recursion to form a
single hunk list. This hunk list is then applied to the original
text.
The text (or binary) fragments are copied directly from their source
Python objects into a preallocated output string to avoid the
allocation of intermediate Python objects. Working memory is about 2x
the total number of hunks.
Copyright 2005 Matt Mackall <mpm@selenic.com>
This software may be used and distributed according to the terms
of the GNU General Public License, incorporated herein by reference.
*/
#include <Python.h>
#include <stdlib.h>
#include <string.h>
#ifdef _WIN32
#ifdef _MSC_VER
#define inline __inline
typedef unsigned long uint32_t;
#else
#include <stdint.h>
#endif
static uint32_t ntohl(uint32_t x)
{
return ((x & 0x000000ffUL) << 24) |
((x & 0x0000ff00UL) << 8) |
((x & 0x00ff0000UL) >> 8) |
((x & 0xff000000UL) >> 24);
}
#else
#include <sys/types.h>
#include <arpa/inet.h>
#endif
static char mpatch_doc[] = "Efficient binary patching.";
struct frag {
int start, end, len;
char *data;
};
struct flist {
struct frag *base, *head, *tail;
};
static struct flist *lalloc(int size)
{
struct flist *a = NULL;
a = malloc(sizeof(struct flist));
if (a) {
a->base = malloc(sizeof(struct frag) * size);
if (!a->base) {
free(a);
a = NULL;
} else
a->head = a->tail = a->base;
}
return a;
}
static void lfree(struct flist *a)
{
if (a) {
free(a->base);
free(a);
}
}
static int lsize(struct flist *a)
{
return a->tail - a->head;
}
/* move hunks in source that are less cut to dest, compensating
for changes in offset. the last hunk may be split if necessary.
*/
static int gather(struct flist *dest, struct flist *src, int cut, int offset)
{
struct frag *d = dest->tail, *s = src->head;
int postend, c, l;
while (s != src->tail) {
if (s->start + offset >= cut)
break; /* we've gone far enough */
postend = offset + s->start + s->len;
if (postend <= cut) {
/* save this hunk */
offset += s->start + s->len - s->end;
*d++ = *s++;
}
else {
/* break up this hunk */
c = cut - offset;
if (s->end < c)
c = s->end;
l = cut - offset - s->start;
if (s->len < l)
l = s->len;
offset += s->start + l - c;
d->start = s->start;
d->end = c;
d->len = l;
d->data = s->data;
d++;
s->start = c;
s->len = s->len - l;
s->data = s->data + l;
break;
}
}
dest->tail = d;
src->head = s;
return offset;
}
/* like gather, but with no output list */
static int discard(struct flist *src, int cut, int offset)
{
struct frag *s = src->head;
int postend, c, l;
while (s != src->tail) {
if (s->start + offset >= cut)
break;
postend = offset + s->start + s->len;
if (postend <= cut) {
offset += s->start + s->len - s->end;
s++;
}
else {
c = cut - offset;
if (s->end < c)
c = s->end;
l = cut - offset - s->start;
if (s->len < l)
l = s->len;
offset += s->start + l - c;
s->start = c;
s->len = s->len - l;
s->data = s->data + l;
break;
}
}
src->head = s;
return offset;
}
/* combine hunk lists a and b, while adjusting b for offset changes in a/
this deletes a and b and returns the resultant list. */
static struct flist *combine(struct flist *a, struct flist *b)
{
struct flist *c = NULL;
struct frag *bh, *ct;
int offset = 0, post;
if (a && b)
c = lalloc((lsize(a) + lsize(b)) * 2);
if (c) {
for (bh = b->head; bh != b->tail; bh++) {
/* save old hunks */
offset = gather(c, a, bh->start, offset);
/* discard replaced hunks */
post = discard(a, bh->end, offset);
/* insert new hunk */
ct = c->tail;
ct->start = bh->start - offset;
ct->end = bh->end - post;
ct->len = bh->len;
ct->data = bh->data;
c->tail++;
offset = post;
}
/* hold on to tail from a */
memcpy(c->tail, a->head, sizeof(struct frag) * lsize(a));
c->tail += lsize(a);
}
lfree(a);
lfree(b);
return c;
}
/* decode a binary patch into a hunk list */
static struct flist *decode(char *bin, int len)
{
struct flist *l;
struct frag *lt;
char *end = bin + len;
char decode[12]; /* for dealing with alignment issues */
/* assume worst case size, we won't have many of these lists */
l = lalloc(len / 12);
lt = l->tail;
while (bin < end) {
memcpy(decode, bin, 12);
lt->start = ntohl(*(uint32_t *)decode);
lt->end = ntohl(*(uint32_t *)(decode + 4));
lt->len = ntohl(*(uint32_t *)(decode + 8));
lt->data = bin + 12;
bin += 12 + lt->len;
lt++;
}
l->tail = lt;
return l;
}
/* calculate the size of resultant text */
static int calcsize(int len, struct flist *l)
{
int outlen = 0, last = 0;
struct frag *f = l->head;
while (f != l->tail) {
outlen += f->start - last;
last = f->end;
outlen += f->len;
f++;
}
outlen += len - last;
return outlen;
}
static void apply(char *buf, char *orig, int len, struct flist *l)
{
struct frag *f = l->head;
int last = 0;
char *p = buf;
while (f != l->tail) {
memcpy(p, orig + last, f->start - last);
p += f->start - last;
memcpy(p, f->data, f->len);
last = f->end;
p += f->len;
f++;
}
memcpy(p, orig + last, len - last);
}
/* recursively generate a patch of all bins between start and end */
static struct flist *fold(PyObject *bins, int start, int end)
{
int len;
if (start + 1 == end) {
/* trivial case, output a decoded list */
PyObject *tmp = PyList_GetItem(bins, start);
if (!tmp)
return NULL;
return decode(PyString_AsString(tmp), PyString_Size(tmp));
}
/* divide and conquer, memory management is elsewhere */
len = (end - start) / 2;
return combine(fold(bins, start, start + len),
fold(bins, start + len, end));
}
static PyObject *
patches(PyObject *self, PyObject *args)
{
PyObject *text, *bins, *result;
struct flist *patch;
char *in, *out;
int len, outlen;
if (!PyArg_ParseTuple(args, "SO:mpatch", &text, &bins))
return NULL;
len = PyList_Size(bins);
if (!len) {
/* nothing to do */
Py_INCREF(text);
return text;
}
patch = fold(bins, 0, len);
if (!patch)
return PyErr_NoMemory();
outlen = calcsize(PyString_Size(text), patch);
result = PyString_FromStringAndSize(NULL, outlen);
if (result) {
in = PyString_AsString(text);
out = PyString_AsString(result);
apply(out, in, PyString_Size(text), patch);
}
lfree(patch);
return result;
}
static PyMethodDef methods[] = {
{"patches", patches, METH_VARARGS, "apply a series of patches\n"},
{NULL, NULL}
};
PyMODINIT_FUNC
initmpatch(void)
{
Py_InitModule3("mpatch", methods, mpatch_doc);
}