[PATCH] Split external diff command interface to a separate file.
[git/git.git] / diff.c
CommitLineData
86436c28
JH
1#include "cache.h"
2#include "diff.h"
3
4static char *diff_cmd = "diff -L 'k/%s' -L 'l/%s' ";
5static char *diff_opts = "-p -u";
6static char *diff_arg_forward = " - '%s'";
7static char *diff_arg_reverse = " '%s' -";
8
9void prepare_diff_cmd(void)
10{
11 /*
12 * Default values above are meant to match the
13 * Linux kernel development style. Examples of
14 * alternative styles you can specify via environment
15 * variables are:
16 *
17 * GIT_DIFF_CMD="diff -L '%s' -L '%s'"
18 * GIT_DIFF_OPTS="-c";
19 */
20 diff_cmd = getenv("GIT_DIFF_CMD") ? : diff_cmd;
21 diff_opts = getenv("GIT_DIFF_OPTS") ? : diff_opts;
22}
23
24/* Help to copy the thing properly quoted for the shell safety.
25 * any single quote is replaced with '\'', and the caller is
26 * expected to enclose the result within a single quote pair.
27 *
28 * E.g.
29 * original sq_expand result
30 * name ==> name ==> 'name'
31 * a b ==> a b ==> 'a b'
32 * a'b ==> a'\''b ==> 'a'\''b'
33 */
34static char *sq_expand(const char *src)
35{
36 static char *buf = NULL;
37 int cnt, c;
38 const char *cp;
39 char *bp;
40
41 /* count bytes needed to store the quoted string. */
42 for (cnt = 1, cp = src; *cp; cnt++, cp++)
43 if (*cp == '\'')
44 cnt += 3;
45
46 if (! (buf = malloc(cnt)))
47 return buf;
48 bp = buf;
49 while ((c = *src++)) {
50 if (c != '\'')
51 *bp++ = c;
52 else {
53 bp = strcpy(bp, "'\\''");
54 bp += 4;
55 }
56 }
57 *bp = 0;
58 return buf;
59}
60
61void show_differences(const char *name, /* filename on the filesystem */
62 const char *label, /* diff label to use */
63 void *old_contents, /* contents in core */
64 unsigned long long old_size, /* size in core */
65 int reverse /* 0: diff core file
66 1: diff file core */)
67{
68 FILE *f;
69 char *name_sq = sq_expand(name);
70 const char *label_sq = (name != label) ? sq_expand(label) : name_sq;
71 char *diff_arg = reverse ? diff_arg_reverse : diff_arg_forward;
72 int cmd_size = strlen(name_sq) + strlen(label_sq) * 2 +
73 strlen(diff_cmd) + strlen(diff_opts) + strlen(diff_arg);
74 char *cmd = malloc(cmd_size);
75 int next_at;
76
77 fflush(stdout);
78 next_at = snprintf(cmd, cmd_size, diff_cmd, label_sq, label_sq);
79 next_at += snprintf(cmd+next_at, cmd_size-next_at, "%s", diff_opts);
80 next_at += snprintf(cmd+next_at, cmd_size-next_at, diff_arg, name_sq);
81 f = popen(cmd, "w");
82 if (old_size)
83 fwrite(old_contents, old_size, 1, f);
84 pclose(f);
85 if (label_sq != name_sq)
86 free((void*)label_sq); /* constness */
87 free(name_sq);
88 free(cmd);
89}
90
91void show_diff_empty(const unsigned char *sha1,
92 const char *name,
93 int reverse)
94{
95 char *old;
96 unsigned long int size;
97 unsigned char type[20];
98
99 old = read_sha1_file(sha1, type, &size);
100 if (! old) {
101 error("unable to read blob object for %s (%s)", name,
102 sha1_to_hex(sha1));
103 return;
104 }
105 show_differences("/dev/null", name, old, size, reverse);
106}