diff.c

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