diff.c

   1 /*
   2  * Copyright (C) 2005 Junio C Hamano
   3  */
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6 #include <signal.h>
   7 #include "cache.h"
   8 #include "diff.h"
   9
  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_OPTS="-c";
  27          */
  28         if (getenv("GIT_EXTERNAL_DIFF"))
  29                 external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
  30
  31         /* In case external diff fails... */
  32         diff_opts = getenv("GIT_DIFF_OPTS") ? : diff_opts;
  33
  34         done_preparing = 1;
  35         return external_diff_cmd;
  36 }
  37
  38 /* Help to copy the thing properly quoted for the shell safety.
  39  * any single quote is replaced with '\'', and the caller is
  40  * expected to enclose the result within a single quote pair.
  41  *
  42  * E.g.
  43  *  original     sq_expand     result
  44  *  name     ==> name      ==> 'name'
  45  *  a b      ==> a b       ==> 'a b'
  46  *  a'b      ==> a'\''b    ==> 'a'\''b'
  47  */
  48 static char *sq_expand(const char *src)
  49 {
  50         static char *buf = NULL;
  51         int cnt, c;
  52         const char *cp;
  53         char *bp;
  54
  55         /* count bytes needed to store the quoted string. */
  56         for (cnt = 1, cp = src; *cp; cnt++, cp++)
  57                 if (*cp == '\'')
  58                         cnt += 3;
  59
  60         buf = xmalloc(cnt);
  61         bp = buf;
  62         while ((c = *src++)) {
  63                 if (c != '\'')
  64                         *bp++ = c;
  65                 else {
  66                         bp = strcpy(bp, "'\\''");
  67                         bp += 4;
  68                 }
  69         }
  70         *bp = 0;
  71         return buf;
  72 }
  73
  74 static struct diff_tempfile {
  75         const char *name;
  76         char hex[41];
  77         char mode[10];
  78         char tmp_path[50];
  79 } diff_temp[2];
  80
  81 static void builtin_diff(const char *name,
  82                          struct diff_tempfile *temp)
  83 {
  84         int i, next_at;
  85         const char *diff_cmd = "diff -L'%s%s%s' -L'%s%s%s'";
  86         const char *diff_arg  = "'%s' '%s'";
  87         const char *input_name_sq[2];
  88         const char *path0[2];
  89         const char *path1[2];
  90         char mode[2][20];
  91         const char *name_sq = sq_expand(name);
  92         char *cmd;
  93
  94         /* diff_cmd and diff_arg have 8 %s in total which makes
  95          * the sum of these strings 16 bytes larger than required.
  96          * we use 2 spaces around diff-opts, and we need to count
  97          * terminating NUL, so we subtract 13 here.
  98          */
  99         int cmd_size = (strlen(diff_cmd) + strlen(diff_opts) +
 100                         strlen(diff_arg) - 13);
 101         for (i = 0; i < 2; i++) {
 102                 input_name_sq[i] = sq_expand(temp[i].name);
 103                 if (!strcmp(temp[i].name, "/dev/null")) {
 104                         path0[i] = "/dev/null";
 105                         path1[i] = "";
 106                         mode[i][0] = 0;
 107                 } else {
 108                         path0[i] = i ? "l/" : "k/";
 109                         path1[i] = name_sq;
 110                         sprintf(mode[i], "  (mode:%s)", temp[i].mode);
 111                 }
 112                 cmd_size += (strlen(path0[i]) + strlen(path1[i]) +
 113                              strlen(mode[i]) + strlen(input_name_sq[i]));
 114         }
 115
 116         cmd = xmalloc(cmd_size);
 117
 118         next_at = 0;
 119         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 120                             diff_cmd,
 121                             path0[0], path1[0], mode[0],
 122                             path0[1], path1[1], mode[1]);
 123         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 124                             " %s ", diff_opts);
 125         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 126                             diff_arg, input_name_sq[0], input_name_sq[1]);
 127
 128         execlp("/bin/sh","sh", "-c", cmd, NULL);
 129 }
 130
 131 static void prepare_temp_file(const char *name,
 132                               struct diff_tempfile *temp,
 133                               struct diff_spec *one)
 134 {
 135         static unsigned char null_sha1[20] = { 0, };
 136
 137         if (!one->file_valid) {
 138         not_a_valid_file:
 139                 /* A '-' entry produces this for file-2, and
 140                  * a '+' entry produces this for file-1.
 141                  */
 142                 temp->name = "/dev/null";
 143                 strcpy(temp->hex, ".");
 144                 strcpy(temp->mode, ".");
 145                 return;
 146         }
 147
 148         if (one->sha1_valid &&
 149             !memcmp(one->u.sha1, null_sha1, sizeof(null_sha1))) {
 150                 one->sha1_valid = 0;
 151                 one->u.name = name;
 152         }
 153
 154         if (!one->sha1_valid) {
 155                 struct stat st;
 156                 temp->name = one->u.name;
 157                 if (stat(temp->name, &st) < 0) {
 158                         if (errno == ENOENT)
 159                                 goto not_a_valid_file;
 160                         die("stat(%s): %s", temp->name, strerror(errno));
 161                 }
 162                 strcpy(temp->hex, sha1_to_hex(null_sha1));
 163                 sprintf(temp->mode, "%06o",
 164                         S_IFREG |ce_permissions(st.st_mode));
 165         }
 166         else {
 167                 int fd;
 168                 void *blob;
 169                 char type[20];
 170                 unsigned long size;
 171
 172                 blob = read_sha1_file(one->u.sha1, type, &size);
 173                 if (!blob || strcmp(type, "blob"))
 174                         die("unable to read blob object for %s (%s)",
 175                             name, sha1_to_hex(one->u.sha1));
 176
 177                 strcpy(temp->tmp_path, ".diff_XXXXXX");
 178                 fd = mkstemp(temp->tmp_path);
 179                 if (fd < 0)
 180                         die("unable to create temp-file");
 181                 if (write(fd, blob, size) != size)
 182                         die("unable to write temp-file");
 183                 close(fd);
 184                 free(blob);
 185                 temp->name = temp->tmp_path;
 186                 strcpy(temp->hex, sha1_to_hex(one->u.sha1));
 187                 temp->hex[40] = 0;
 188                 sprintf(temp->mode, "%06o", one->mode);
 189         }
 190 }
 191
 192 static void remove_tempfile(void)
 193 {
 194         int i;
 195
 196         for (i = 0; i < 2; i++)
 197                 if (diff_temp[i].name == diff_temp[i].tmp_path) {
 198                         unlink(diff_temp[i].name);
 199                         diff_temp[i].name = NULL;
 200                 }
 201 }
 202
 203 static void remove_tempfile_on_signal(int signo)
 204 {
 205         remove_tempfile();
 206 }
 207
 208 /* An external diff command takes:
 209  *
 210  * diff-cmd name infile1 infile1-sha1 infile1-mode \
 211  *               infile2 infile2-sha1 infile2-mode.
 212  *
 213  */
 214 void run_external_diff(const char *name,
 215                        struct diff_spec *one,
 216                        struct diff_spec *two)
 217 {
 218         struct diff_tempfile *temp = diff_temp;
 219         pid_t pid;
 220         int status;
 221         static int atexit_asked = 0;
 222
 223         if (one && two) {
 224                 prepare_temp_file(name, &temp[0], one);
 225                 prepare_temp_file(name, &temp[1], two);
 226                 if (! atexit_asked &&
 227                     (temp[0].name == temp[0].tmp_path ||
 228                      temp[1].name == temp[1].tmp_path)) {
 229                         atexit_asked = 1;
 230                         atexit(remove_tempfile);
 231                 }
 232                 signal(SIGINT, remove_tempfile_on_signal);
 233         }
 234
 235         fflush(NULL);
 236         pid = fork();
 237         if (pid < 0)
 238                 die("unable to fork");
 239         if (!pid) {
 240                 const char *pgm = external_diff();
 241                 if (pgm) {
 242                         if (one && two)
 243                                 execlp(pgm, pgm,
 244                                        name,
 245                                        temp[0].name, temp[0].hex, temp[0].mode,
 246                                        temp[1].name, temp[1].hex, temp[1].mode,
 247                                        NULL);
 248                         else
 249                                 execlp(pgm, pgm, name, NULL);
 250                 }
 251                 /*
 252                  * otherwise we use the built-in one.
 253                  */
 254                 if (one && two)
 255                         builtin_diff(name, temp);
 256                 else
 257                         printf("* Unmerged path %s\n", name);
 258                 exit(0);
 259         }
 260         if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status)) {
 261                 /* We do not check the exit status because typically
 262                  * diff exits non-zero if files are different, and
 263                  * we are not interested in knowing that.  We *knew*
 264                  * they are different and that's why we ran diff
 265                  * in the first place!  However if it dies by a signal,
 266                  * we stop processing immediately.
 267                  */
 268                 remove_tempfile();
 269                 die("external diff died unexpectedly.\n");
 270         }
 271         remove_tempfile();
 272 }
 273
 274 void diff_addremove(int addremove, unsigned mode,
 275                     const unsigned char *sha1,
 276                     const char *base, const char *path)
 277 {
 278         char concatpath[PATH_MAX];
 279         struct diff_spec spec[2], *one, *two;
 280
 281         memcpy(spec[0].u.sha1, sha1, 20);
 282         spec[0].mode = mode;
 283         spec[0].sha1_valid = spec[0].file_valid = 1;
 284         spec[1].file_valid = 0;
 285
 286         if (addremove == '+') {
 287                 one = spec + 1; two = spec;
 288         } else {
 289                 one = spec; two = one + 1;
 290         }
 291
 292         if (path) {
 293                 strcpy(concatpath, base);
 294                 strcat(concatpath, path);
 295         }
 296         run_external_diff(path ? concatpath : base, one, two);
 297 }
 298
 299 void diff_change(unsigned old_mode, unsigned new_mode,
 300                  const unsigned char *old_sha1,
 301                  const unsigned char *new_sha1,
 302                  const char *base, const char *path) {
 303         char concatpath[PATH_MAX];
 304         struct diff_spec spec[2];
 305
 306         memcpy(spec[0].u.sha1, old_sha1, 20);
 307         spec[0].mode = old_mode;
 308         memcpy(spec[1].u.sha1, new_sha1, 20);
 309         spec[1].mode = new_mode;
 310         spec[0].sha1_valid = spec[0].file_valid = 1;
 311         spec[1].sha1_valid = spec[1].file_valid = 1;
 312
 313         if (path) {
 314                 strcpy(concatpath, base);
 315                 strcat(concatpath, path);
 316         }
 317         run_external_diff(path ? concatpath : base, &spec[0], &spec[1]);
 318 }
 319
 320 void diff_unmerge(const char *path)
 321 {
 322         run_external_diff(path, NULL, NULL);
 323 }