atomicupdate: add an experimental option to use atomictemp when updating In some cases Mercurial truncating files when updating causes problems. It can happens when processes are currently reading the file or with big file or on NFS mounts. We add an experimental option to use the atomictemp option of vfs.__call__ in order to avoid the problem. The localrepository.wwrite seems to assume the files are created without the `x` flag; with atomictempfile, the new file might inherit the `x` flag from the destination. We force remove it afterward. This code could be refactored and the flag processing could be moved inside vfs. This patch should be tested with `--extra-config-opt experimental.update.atomic-file=True` as we disabled the option by default. Differential Revision: https://phab.mercurial-scm.org/D1882

#ifndef _HG_BDIFF_H_
#define _HG_BDIFF_H_

#include "compat.h"

struct bdiff_line {
	int hash, n, e;
	ssize_t len;
	const char *l;
};

struct bdiff_hunk;
struct bdiff_hunk {
	int a1, a2, b1, b2;
	struct bdiff_hunk *next;
};

int bdiff_splitlines(const char *a, ssize_t len, struct bdiff_line **lr);
int bdiff_diff(struct bdiff_line *a, int an, struct bdiff_line *b, int bn,
               struct bdiff_hunk *base);
void bdiff_freehunks(struct bdiff_hunk *l);

#endif