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
===================================================================
/*
bdiff.c - efficient binary diff extension for Mercurial
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.
Based roughly on Python difflib
*/
#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 htonl(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
struct line {
int h, len, n, e;
const char *l;
};
struct pos {
int pos, len;
};
struct hunk {
int a1, a2, b1, b2;
};
struct hunklist {
struct hunk *base, *head;
};
static __inline uint32_t rol32(uint32_t word, unsigned int shift)
{
return (word << shift) | (word >> (32 - shift));
}
int splitlines(const char *a, int len, struct line **lr)
{
int h, i;
const char *p, *b = a;
struct line *l;
/* count the lines */
i = 1; /* extra line for sentinel */
for (p = a; p < a + len; p++)
if (*p == '\n' || p == a + len - 1)
i++;
*lr = l = malloc(sizeof(struct line) * i);
if (!l)
return -1;
/* build the line array and calculate hashes */
h = 0;
for (p = a; p < a + len; p++) {
h = *p + rol32(h, 7); /* a simple hash from GNU diff */
if (*p == '\n' || p == a + len - 1) {
l->len = p - b + 1;
l->h = h * l->len;
l->l = b;
l->n = -1;
l++;
b = p + 1;
h = 0;
}
}
/* set up a sentinel */
l->h = l->len = 0;
l->l = a + len;
return i - 1;
}
int inline cmp(struct line *a, struct line *b)
{
return a->h != b->h || a->len != b->len || memcmp(a->l, b->l, a->len);
}
static int equatelines(struct line *a, int an, struct line *b, int bn)
{
int i, j, buckets = 1, t;
struct pos *h;
/* build a hash table of the next highest power of 2 */
while (buckets < bn + 1)
buckets *= 2;
h = malloc(buckets * sizeof(struct pos));
buckets = buckets - 1;
if (!h)
return 0;
/* clear the hash table */
for (i = 0; i <= buckets; i++) {
h[i].pos = -1;
h[i].len = 0;
}
/* add lines to the hash table chains */
for (i = bn - 1; i >= 0; i--) {
/* find the equivalence class */
for (j = b[i].h & buckets; h[j].pos != -1;
j = (j + 1) & buckets)
if (!cmp(b + i, b + h[j].pos))
break;
/* add to the head of the equivalence class */
b[i].n = h[j].pos;
b[i].e = j;
h[j].pos = i;
h[j].len++; /* keep track of popularity */
}
/* compute popularity threshold */
t = (bn >= 200) ? bn / 100 : bn + 1;
/* match items in a to their equivalence class in b */
for (i = 0; i < an; i++) {
/* find the equivalence class */
for (j = a[i].h & buckets; h[j].pos != -1;
j = (j + 1) & buckets)
if (!cmp(a + i, b + h[j].pos))
break;
a[i].e = j; /* use equivalence class for quick compare */
if(h[j].len <= t)
a[i].n = h[j].pos; /* point to head of match list */
else
a[i].n = -1; /* too popular */
}
/* discard hash tables */
free(h);
return 1;
}
static int longest_match(struct line *a, struct line *b, struct pos *pos,
int a1, int a2, int b1, int b2, int *omi, int *omj)
{
int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k;
for (i = a1; i < a2; i++) {
/* skip things before the current block */
for (j = a[i].n; j != -1 && j < b1; j = b[j].n)
;
/* loop through all lines match a[i] in b */
for (; j != -1 && j < b2; j = b[j].n) {
/* does this extend an earlier match? */
if (i > a1 && j > b1 && pos[j - 1].pos == i - 1)
k = pos[j - 1].len + 1;
else
k = 1;
pos[j].pos = i;
pos[j].len = k;
/* best match so far? */
if (k > mk) {
mi = i;
mj = j;
mk = k;
}
}
}
if (mk) {
mi = mi - mk + 1;
mj = mj - mk + 1;
}
/* expand match to include neighboring popular lines */
while (mi - mb > a1 && mj - mb > b1 &&
a[mi - mb - 1].e == b[mj - mb - 1].e)
mb++;
while (mi + mk < a2 && mj + mk < b2 &&
a[mi + mk].e == b[mj + mk].e)
mk++;
*omi = mi - mb;
*omj = mj - mb;
return mk + mb;
}
static void recurse(struct line *a, struct line *b, struct pos *pos,
int a1, int a2, int b1, int b2, struct hunklist *l)
{
int i, j, k;
/* find the longest match in this chunk */
k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j);
if (!k)
return;
/* and recurse on the remaining chunks on either side */
recurse(a, b, pos, a1, i, b1, j, l);
l->head->a1 = i;
l->head->a2 = i + k;
l->head->b1 = j;
l->head->b2 = j + k;
l->head++;
recurse(a, b, pos, i + k, a2, j + k, b2, l);
}
static struct hunklist diff(struct line *a, int an, struct line *b, int bn)
{
struct hunklist l;
struct pos *pos;
int t;
/* allocate and fill arrays */
t = equatelines(a, an, b, bn);
pos = calloc(bn, sizeof(struct pos));
l.head = l.base = malloc(sizeof(struct hunk) * ((an + bn) / 4 + 2));
if (pos && l.base && t) {
/* generate the matching block list */
recurse(a, b, pos, 0, an, 0, bn, &l);
l.head->a1 = an;
l.head->b1 = bn;
l.head++;
}
free(pos);
return l;
}
static PyObject *blocks(PyObject *self, PyObject *args)
{
PyObject *sa, *sb, *rl = NULL, *m;
struct line *a, *b;
struct hunklist l;
struct hunk *h;
int an, bn, pos = 0;
if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb))
return NULL;
an = splitlines(PyString_AsString(sa), PyString_Size(sa), &a);
bn = splitlines(PyString_AsString(sb), PyString_Size(sb), &b);
if (!a || !b)
goto nomem;
l = diff(a, an, b, bn);
rl = PyList_New(l.head - l.base);
if (!l.head || !rl)
goto nomem;
for(h = l.base; h != l.head; h++) {
m = Py_BuildValue("iiii", h->a1, h->a2, h->b1, h->b2);
PyList_SetItem(rl, pos, m);
pos++;
}
nomem:
free(a);
free(b);
free(l.base);
return rl ? rl : PyErr_NoMemory();
}
static PyObject *bdiff(PyObject *self, PyObject *args)
{
PyObject *sa, *sb, *result = NULL;
struct line *al, *bl;
struct hunklist l;
struct hunk *h;
char encode[12], *rb;
int an, bn, len = 0, la = 0, lb = 0;
if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb))
return NULL;
an = splitlines(PyString_AsString(sa), PyString_Size(sa), &al);
bn = splitlines(PyString_AsString(sb), PyString_Size(sb), &bl);
if (!al || !bl)
goto nomem;
l = diff(al, an, bl, bn);
if (!l.head)
goto nomem;
/* calculate length of output */
for(h = l.base; h != l.head; h++) {
if (h->a1 != la || h->b1 != lb)
len += 12 + bl[h->b1].l - bl[lb].l;
la = h->a2;
lb = h->b2;
}
result = PyString_FromStringAndSize(NULL, len);
if (!result)
goto nomem;
/* build binary patch */
rb = PyString_AsString(result);
la = lb = 0;
for(h = l.base; h != l.head; h++) {
if (h->a1 != la || h->b1 != lb) {
len = bl[h->b1].l - bl[lb].l;
*(uint32_t *)(encode) = htonl(al[la].l - al->l);
*(uint32_t *)(encode + 4) = htonl(al[h->a1].l - al->l);
*(uint32_t *)(encode + 8) = htonl(len);
memcpy(rb, encode, 12);
memcpy(rb + 12, bl[lb].l, len);
rb += 12 + len;
}
la = h->a2;
lb = h->b2;
}
nomem:
free(al);
free(bl);
free(l.base);
return result ? result : PyErr_NoMemory();
}
static char mdiff_doc[] = "Efficient binary diff.";
static PyMethodDef methods[] = {
{"bdiff", bdiff, METH_VARARGS, "calculate a binary diff\n"},
{"blocks", blocks, METH_VARARGS, "find a list of matching lines\n"},
{NULL, NULL}
};
PyMODINIT_FUNC initbdiff(void)
{
Py_InitModule3("bdiff", methods, mdiff_doc);
}