summaryrefslogtreecommitdiff
path: root/diff.c
blob: 9905cdb0122afecc282273c0e728c3f3b75fc51d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include <sys/types.h>
#include <sys/wait.h>
#include "cache.h"
#include "diff.h"
 
static char *diff_cmd = "diff -L'k/%s' -L'l/%s'";
static char *diff_opts = "-pu";
 
static const char *external_diff(void)
{
	static char *external_diff_cmd = NULL;
	static int done_preparing = 0;
 
	if (done_preparing)
		return external_diff_cmd;
 
	/*
	 * Default values above are meant to match the
	 * Linux kernel development style.  Examples of
	 * alternative styles you can specify via environment
	 * variables are:
	 *
	 * GIT_DIFF_CMD="diff -L '%s' -L '%s'"
	 * GIT_DIFF_OPTS="-c";
	 */
	if (getenv("GIT_EXTERNAL_DIFF"))
		external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
 
	/* In case external diff fails... */
	diff_cmd = getenv("GIT_DIFF_CMD") ? : diff_cmd;
	diff_opts = getenv("GIT_DIFF_OPTS") ? : diff_opts;
 
	done_preparing = 1;
	return external_diff_cmd;
}
 
/* Help to copy the thing properly quoted for the shell safety.
 * any single quote is replaced with '\'', and the caller is
 * expected to enclose the result within a single quote pair.
 *
 * E.g.
 *  original     sq_expand     result
 *  name     ==> name      ==> 'name'
 *  a b      ==> a b       ==> 'a b'
 *  a'b      ==> a'\''b    ==> 'a'\''b'
 */
static char *sq_expand(const char *src)
{
	static char *buf = NULL;
	int cnt, c;
	const char *cp;
	char *bp;
 
	/* count bytes needed to store the quoted string. */ 
	for (cnt = 1, cp = src; *cp; cnt++, cp++)
		if (*cp == '\'')
			cnt += 3;
 
	if (! (buf = malloc(cnt)))
	    return buf;
	bp = buf;
	while ((c = *src++)) {
		if (c != '\'')
			*bp++ = c;
		else {
			bp = strcpy(bp, "'\\''");
			bp += 4;
		}
	}
	*bp = 0;
	return buf;
}
 
static struct diff_tempfile {
	const char *name;
	char hex[41];
	char mode[10];
	char tmp_path[50];
} diff_temp[2];
 
static void builtin_diff(const char *name,
			 struct diff_tempfile *temp)
{
	static char *diff_arg  = "'%s' '%s'";
	const char *name_1_sq = sq_expand(temp[0].name);
	const char *name_2_sq = sq_expand(temp[1].name);
	const char *name_sq = sq_expand(name);
 
	/* diff_cmd and diff_arg have 4 %s in total which makes
	 * the sum of these strings 8 bytes larger than required.
	 * we use 2 spaces around diff-opts, and we need to count
	 * terminating NUL, so we subtract 5 here.
	 */
	int cmd_size = (strlen(diff_cmd) + 
			strlen(name_sq) * 2 +
			strlen(diff_opts) +
			strlen(diff_arg) +
			strlen(name_1_sq) + strlen(name_2_sq)
			- 5);
	char *cmd = malloc(cmd_size);
	int next_at = 0;
 
	next_at += snprintf(cmd+next_at, cmd_size-next_at,
			    diff_cmd, name_sq, name_sq);
	next_at += snprintf(cmd+next_at, cmd_size-next_at,
			    " %s ", diff_opts);
	next_at += snprintf(cmd+next_at, cmd_size-next_at,
			    diff_arg, name_1_sq, name_2_sq);
	execlp("/bin/sh","sh", "-c", cmd, NULL);
}
 
static void prepare_temp_file(const char *name,
			      struct diff_tempfile *temp,
			      struct diff_spec *one)
{
	static unsigned char null_sha1[20] = { 0, };
 
	if (!one->file_valid) {
	not_a_valid_file:
		temp->name = "/dev/null";
		strcpy(temp->hex, ".");
		strcpy(temp->mode, ".");
		return;
	}
 
	if (one->sha1_valid &&
	    !memcmp(one->u.sha1, null_sha1, sizeof(null_sha1))) {
		one->sha1_valid = 0;
		one->u.name = name;
	}
 
	if (!one->sha1_valid) {
		struct stat st;
		temp->name = one->u.name;
		if (stat(temp->name, &st) < 0) {
			if (errno == ENOENT)
				goto not_a_valid_file;
			die("stat(%s): %s", temp->name, strerror(errno));
		}
		strcpy(temp->hex, ".");
		sprintf(temp->mode, "%06o",
			S_IFREG |ce_permissions(st.st_mode));
	}
	else {
		int fd;
		void *blob;
		char type[20];
		unsigned long size;
 
		blob = read_sha1_file(one->u.sha1, type, &size);
		if (!blob || strcmp(type, "blob"))
			die("unable to read blob object for %s (%s)",
			    name, sha1_to_hex(one->u.sha1));
 
		strcpy(temp->tmp_path, ".diff_XXXXXX");
		fd = mkstemp(temp->tmp_path);
		if (fd < 0)
			die("unable to create temp-file");
		if (write(fd, blob, size) != size)
			die("unable to write temp-file");
		close(fd);
		free(blob);
		temp->name = temp->tmp_path;
		strcpy(temp->hex, sha1_to_hex(one->u.sha1));
		temp->hex[40] = 0;
		sprintf(temp->mode, "%06o", one->mode);
	}
}
 
static void remove_tempfile(void)
{
	int i;
 
	for (i = 0; i < 2; i++)
		if (diff_temp[i].name == diff_temp[i].tmp_path) {
			unlink(diff_temp[i].name);
			diff_temp[i].name = NULL;
		}
}
 
/* An external diff command takes:
 *
 * diff-cmd name infile1 infile1-sha1 infile1-mode \
 *               infile2 infile2-sha1 infile2-mode.
 *
 */
void run_external_diff(const char *name,
		       struct diff_spec *one,
		       struct diff_spec *two)
{
	struct diff_tempfile *temp = diff_temp;
	int pid, status;
	static int atexit_asked = 0;
 
	prepare_temp_file(name, &temp[0], one);
	prepare_temp_file(name, &temp[1], two);
	if (! atexit_asked &&
	    (temp[0].name == temp[0].tmp_path ||
	     temp[1].name == temp[1].tmp_path)) {
		atexit_asked = 1;
		atexit(remove_tempfile);
	}
 
	fflush(NULL);
	pid = fork();
	if (pid < 0)
		die("unable to fork");
	if (!pid) {
		const char *pgm = external_diff();
		if (pgm)
			execlp(pgm, pgm,
			       name,
			       temp[0].name, temp[0].hex, temp[0].mode,
			       temp[1].name, temp[1].hex, temp[1].mode,
			       NULL);
		/*
		 * otherwise we use the built-in one.
		 */
		builtin_diff(name, temp);
		exit(0);
	}
	if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status))
		die("diff program failed");
 
	remove_tempfile();
}
 
void show_diff_empty(const struct cache_entry *ce, int reverse)
{
	struct diff_spec spec[2], *one, *two;
 
	memcpy(spec[0].u.sha1, ce->sha1, 20);
	spec[0].mode = ntohl(ce->ce_mode);
	spec[0].sha1_valid = spec[0].file_valid = 1;
	spec[1].file_valid = 0;
 
	if (reverse) {
		one = spec + 1; two = spec;
	} else {
		one = spec; two = one + 1;
	}
 
	run_external_diff(ce->name, one, two);
}
 
void show_differences(const struct cache_entry *ce, int reverse) 
{
	struct diff_spec spec[2], *one, *two;
 
	memcpy(spec[0].u.sha1, ce->sha1, 20);
	spec[0].mode = ntohl(ce->ce_mode);
	spec[0].sha1_valid = spec[0].file_valid = 1;
 
	spec[1].u.name = ce->name; /* the name we stated */
	spec[1].sha1_valid = 0;
	spec[1].file_valid = 1;
 
	if (reverse) {
		one = spec + 1; two = spec;
	} else {
		one = spec; two = one + 1;
	}
 
	run_external_diff(ce->name, one, two);
}