Mercurial > hg
view mercurial/bdiff.c @ 28029:72072cfc7e91
update: warn about other topological heads on bare update
A concern around the user experience of Mercurial is user getting stuck on there
own topological branch forever. For example, someone pulling another topological
branch, missing that message in pull asking them to merge and getting stuck on
there own local branch.
The current way to "address" this concern was for bare 'hg update' to target the
tipmost (also latest pulled) changesets and complain when the update was not
linear. That way, failure to merge newly pulled changesets would result in some
kind of failure.
Yet the failure was quite obscure, not working in all cases (eg: commit right
after pull) and the behavior was very impractical in the common case
(eg: issue4673).
To be able to change that behavior, we need to provide other ways to alert a
user stucks on one of many topological head. We do so with an extra message after
bare update:
1 other heads for branch "default"
Bookmark get its own special version:
1 other divergent bookmarks for "foobar"
There is significant room to improve the message itself, and we should augment
it with hint about how to see theses other heads or handle the situation (see
in-line comment). But having "a" message is already a significant improvement
compared to the existing situation. Once we have it we can iterate on a better
version of it. As having such message is an important step toward changing the
default destination for update and other nicety, I would like to move forward
quickly on getting such message.
This was discussed during London - October 2015 Sprint.
author | Pierre-Yves David <pierre-yves.david@fb.com> |
---|---|
date | Tue, 02 Feb 2016 14:49:02 +0000 |
parents | 66b21ce60a19 |
children | e868d8ee7c8f |
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/* bdiff.c - efficient binary diff extension for Mercurial Copyright 2005, 2006 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 */ #define PY_SSIZE_T_CLEAN #include <Python.h> #include <stdlib.h> #include <string.h> #include <limits.h> #include "util.h" struct line { int hash, n, e; Py_ssize_t len; const char *l; }; struct pos { int pos, len; }; struct hunk; struct hunk { int a1, a2, b1, b2; struct hunk *next; }; static int splitlines(const char *a, Py_ssize_t len, struct line **lr) { unsigned hash; int i; const char *p, *b = a; const char * const plast = a + len - 1; struct line *l; /* count the lines */ i = 1; /* extra line for sentinel */ for (p = a; p < a + len; p++) if (*p == '\n' || p == plast) i++; *lr = l = (struct line *)malloc(sizeof(struct line) * i); if (!l) return -1; /* build the line array and calculate hashes */ hash = 0; for (p = a; p < a + len; p++) { /* Leonid Yuriev's hash */ hash = (hash * 1664525) + (unsigned char)*p + 1013904223; if (*p == '\n' || p == plast) { l->hash = hash; hash = 0; l->len = p - b + 1; l->l = b; l->n = INT_MAX; l++; b = p + 1; } } /* set up a sentinel */ l->hash = 0; l->len = 0; l->l = a + len; return i - 1; } static inline int cmp(struct line *a, struct line *b) { return a->hash != b->hash || 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, scale; struct pos *h = NULL; /* build a hash table of the next highest power of 2 */ while (buckets < bn + 1) buckets *= 2; /* try to allocate a large hash table to avoid collisions */ for (scale = 4; scale; scale /= 2) { h = (struct pos *)malloc(scale * buckets * sizeof(struct pos)); if (h) break; } if (!h) return 0; buckets = buckets * scale - 1; /* clear the hash table */ for (i = 0; i <= buckets; i++) { h[i].pos = INT_MAX; 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].hash & buckets; h[j].pos != INT_MAX; 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 >= 31000) ? bn / 1000 : 1000000 / (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].hash & buckets; h[j].pos != INT_MAX; 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 = INT_MAX; /* 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 < b1; j = b[j].n) ; /* loop through all lines match a[i] in b */ for (; 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 struct hunk *recurse(struct line *a, struct line *b, struct pos *pos, int a1, int a2, int b1, int b2, struct hunk *l) { int i, j, k; while (1) { /* find the longest match in this chunk */ k = longest_match(a, b, pos, a1, a2, b1, b2, &i, &j); if (!k) return l; /* and recurse on the remaining chunks on either side */ l = recurse(a, b, pos, a1, i, b1, j, l); if (!l) return NULL; l->next = (struct hunk *)malloc(sizeof(struct hunk)); if (!l->next) return NULL; l = l->next; l->a1 = i; l->a2 = i + k; l->b1 = j; l->b2 = j + k; l->next = NULL; /* tail-recursion didn't happen, so do equivalent iteration */ a1 = i + k; b1 = j + k; } } static int diff(struct line *a, int an, struct line *b, int bn, struct hunk *base) { struct hunk *curr; struct pos *pos; int t, count = 0; /* allocate and fill arrays */ t = equatelines(a, an, b, bn); pos = (struct pos *)calloc(bn ? bn : 1, sizeof(struct pos)); if (pos && t) { /* generate the matching block list */ curr = recurse(a, b, pos, 0, an, 0, bn, base); if (!curr) return -1; /* sentinel end hunk */ curr->next = (struct hunk *)malloc(sizeof(struct hunk)); if (!curr->next) return -1; curr = curr->next; curr->a1 = curr->a2 = an; curr->b1 = curr->b2 = bn; curr->next = NULL; } free(pos); /* normalize the hunk list, try to push each hunk towards the end */ for (curr = base->next; curr; curr = curr->next) { struct hunk *next = curr->next; int shift = 0; if (!next) break; if (curr->a2 == next->a1) while (curr->a2 + shift < an && curr->b2 + shift < bn && !cmp(a + curr->a2 + shift, b + curr->b2 + shift)) shift++; else if (curr->b2 == next->b1) while (curr->b2 + shift < bn && curr->a2 + shift < an && !cmp(b + curr->b2 + shift, a + curr->a2 + shift)) shift++; if (!shift) continue; curr->b2 += shift; next->b1 += shift; curr->a2 += shift; next->a1 += shift; } for (curr = base->next; curr; curr = curr->next) count++; return count; } static void freehunks(struct hunk *l) { struct hunk *n; for (; l; l = n) { n = l->next; free(l); } } static PyObject *blocks(PyObject *self, PyObject *args) { PyObject *sa, *sb, *rl = NULL, *m; struct line *a, *b; struct hunk l, *h; int an, bn, count, pos = 0; l.next = NULL; if (!PyArg_ParseTuple(args, "SS:bdiff", &sa, &sb)) return NULL; an = splitlines(PyBytes_AsString(sa), PyBytes_Size(sa), &a); bn = splitlines(PyBytes_AsString(sb), PyBytes_Size(sb), &b); if (!a || !b) goto nomem; count = diff(a, an, b, bn, &l); if (count < 0) goto nomem; rl = PyList_New(count); if (!rl) goto nomem; for (h = l.next; h; h = h->next) { m = Py_BuildValue("iiii", h->a1, h->a2, h->b1, h->b2); PyList_SetItem(rl, pos, m); pos++; } nomem: free(a); free(b); freehunks(l.next); return rl ? rl : PyErr_NoMemory(); } static PyObject *bdiff(PyObject *self, PyObject *args) { char *sa, *sb, *rb; PyObject *result = NULL; struct line *al, *bl; struct hunk l, *h; int an, bn, count; Py_ssize_t len = 0, la, lb; PyThreadState *_save; l.next = NULL; if (!PyArg_ParseTuple(args, "s#s#:bdiff", &sa, &la, &sb, &lb)) return NULL; if (la > UINT_MAX || lb > UINT_MAX) { PyErr_SetString(PyExc_ValueError, "bdiff inputs too large"); return NULL; } _save = PyEval_SaveThread(); an = splitlines(sa, la, &al); bn = splitlines(sb, lb, &bl); if (!al || !bl) goto nomem; count = diff(al, an, bl, bn, &l); if (count < 0) goto nomem; /* calculate length of output */ la = lb = 0; for (h = l.next; h; h = h->next) { if (h->a1 != la || h->b1 != lb) len += 12 + bl[h->b1].l - bl[lb].l; la = h->a2; lb = h->b2; } PyEval_RestoreThread(_save); _save = NULL; result = PyBytes_FromStringAndSize(NULL, len); if (!result) goto nomem; /* build binary patch */ rb = PyBytes_AsString(result); la = lb = 0; for (h = l.next; h; h = h->next) { if (h->a1 != la || h->b1 != lb) { len = bl[h->b1].l - bl[lb].l; putbe32((uint32_t)(al[la].l - al->l), rb); putbe32((uint32_t)(al[h->a1].l - al->l), rb + 4); putbe32((uint32_t)len, rb + 8); memcpy(rb + 12, bl[lb].l, len); rb += 12 + len; } la = h->a2; lb = h->b2; } nomem: if (_save) PyEval_RestoreThread(_save); free(al); free(bl); freehunks(l.next); return result ? result : PyErr_NoMemory(); } /* * If allws != 0, remove all whitespace (' ', \t and \r). Otherwise, * reduce whitespace sequences to a single space and trim remaining whitespace * from end of lines. */ static PyObject *fixws(PyObject *self, PyObject *args) { PyObject *s, *result = NULL; char allws, c; const char *r; Py_ssize_t i, rlen, wlen = 0; char *w; if (!PyArg_ParseTuple(args, "Sb:fixws", &s, &allws)) return NULL; r = PyBytes_AsString(s); rlen = PyBytes_Size(s); w = (char *)malloc(rlen ? rlen : 1); if (!w) goto nomem; for (i = 0; i != rlen; i++) { c = r[i]; if (c == ' ' || c == '\t' || c == '\r') { if (!allws && (wlen == 0 || w[wlen - 1] != ' ')) w[wlen++] = ' '; } else if (c == '\n' && !allws && wlen > 0 && w[wlen - 1] == ' ') { w[wlen - 1] = '\n'; } else { w[wlen++] = c; } } result = PyBytes_FromStringAndSize(w, wlen); nomem: free(w); 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"}, {"fixws", fixws, METH_VARARGS, "normalize diff whitespaces\n"}, {NULL, NULL} }; #ifdef IS_PY3K static struct PyModuleDef bdiff_module = { PyModuleDef_HEAD_INIT, "bdiff", mdiff_doc, -1, methods }; PyMODINIT_FUNC PyInit_bdiff(void) { return PyModule_Create(&bdiff_module); } #else PyMODINIT_FUNC initbdiff(void) { Py_InitModule3("bdiff", methods, mdiff_doc); } #endif