mercurial/mpatch.h

filemerge: make last line of prompts <40 english chars (issue6158)

I've chosen <40 as the target so that other languages that may have a 2x blowup
in character count can still have a chance to fit into an 80 column screen.

Previously, we would show a prompt like:

```
keep (l)ocal [dest], take (o)ther [source], or leave (u)nresolved for some/potentially/really/long/path?
```

On at least some systems, if readline was in use then the last line of the
prompt would be wrapped strangely if it couldn't fit entirely on one line. This
strange wrapping may be just a carriage return without a line feed, overwriting
the beginning of the line; example (100 columns wide, 65 character filename, and
yes there's 10 spaces on the end, I assume this is to handle the user inputting
longest word we provide as an option, "unresolved"):

```
ng/dir/name/that/does/not/work/well/with/readline/file.txt? ave (u)nresolved for some/lon
```

In some cases it may partially wrap onto the next line, but still be missing
earlier parts in the line, such as below (60 columns wide, 65 character
filename):

```
 rev], or leave (u)nresolved for some/long/dir/name/that/do
s/not/work/well/with/readline/file.txt?
```

With this fix, this looks like this on a 60 column screen:

```
tool vim_with_markers (for pattern some/long/dir/name/that/d
oes/not/work/well/with/readline/file.txt) can't handle binar
y
tool meld can't handle binary
tool vim_with_markers can't handle binary
tool internal:merge3 can't handle binary
tool merge can't handle binary
no tool found to merge some/long/dir/name/that/does/not/work
/well/with/readline/file.txt
file 'some/long/dir/name/that/does/not/work/well/with/readli
ne/file.txt' needs to be resolved.
You can keep (l)ocal [working copy], take (o)ther [merge rev
], or leave (u)nresolved.
What do you want to do?
```

Differential Revision: https://phab.mercurial-scm.org/D6562

#ifndef _HG_MPATCH_H_
#define _HG_MPATCH_H_

#define MPATCH_ERR_NO_MEM -3
#define MPATCH_ERR_CANNOT_BE_DECODED -2
#define MPATCH_ERR_INVALID_PATCH -1

struct mpatch_frag {
	int start, end, len;
	const char *data;
};

struct mpatch_flist {
	struct mpatch_frag *base, *head, *tail;
};

int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res);
ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l);
void mpatch_lfree(struct mpatch_flist *a);
int mpatch_apply(char *buf, const char *orig, ssize_t len,
                 struct mpatch_flist *l);
struct mpatch_flist *
mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t),
            ssize_t start, ssize_t end);

#endif