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' -L'%s%s'";
  86         const char *diff_arg  = "'%s' '%s'||:"; /* "||:" is to return 0 */
  87         const char *input_name_sq[2];
  88         const char *path0[2];
  89         const char *path1[2];
  90         const char *name_sq = sq_expand(name);
  91         char *cmd;
  92
  93         /* diff_cmd and diff_arg have 6 %s in total which makes
  94          * the sum of these strings 12 bytes larger than required.
  95          * we use 2 spaces around diff-opts, and we need to count
  96          * terminating NUL, so we subtract 9 here.
  97          */
  98         int cmd_size = (strlen(diff_cmd) + strlen(diff_opts) +
  99                         strlen(diff_arg) - 9);
 100         for (i = 0; i < 2; i++) {
 101                 input_name_sq[i] = sq_expand(temp[i].name);
 102                 if (!strcmp(temp[i].name, "/dev/null")) {
 103                         path0[i] = "/dev/null";
 104                         path1[i] = "";
 105                 } else {
 106                         path0[i] = i ? "b/" : "a/";
 107                         path1[i] = name_sq;
 108                 }
 109                 cmd_size += (strlen(path0[i]) + strlen(path1[i]) +
 110                              strlen(input_name_sq[i]));
 111         }
 112
 113         cmd = xmalloc(cmd_size);
 114
 115         next_at = 0;
 116         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 117                             diff_cmd,
 118                             path0[0], path1[0], path0[1], path1[1]);
 119         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 120                             " %s ", diff_opts);
 121         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 122                             diff_arg, input_name_sq[0], input_name_sq[1]);
 123
 124         if (!path1[0][0])
 125                 printf("Created: %s (mode:%s)\n", name, temp[1].mode);
 126         else if (!path1[1][0])
 127                 printf("Deleted: %s\n", name);
 128         else if (strcmp(temp[0].mode, temp[1].mode))
 129                 printf("Mode changed: %s (%s->%s)\n", name,
 130                        temp[0].mode, temp[1].mode);
 131         fflush(NULL);
 132         execlp("/bin/sh","sh", "-c", cmd, NULL);
 133 }
 134
 135 static void prepare_temp_file(const char *name,
 136                               struct diff_tempfile *temp,
 137                               struct diff_spec *one)
 138 {
 139         static unsigned char null_sha1[20] = { 0, };
 140
 141         if (!one->file_valid) {
 142         not_a_valid_file:
 143                 /* A '-' entry produces this for file-2, and
 144                  * a '+' entry produces this for file-1.
 145                  */
 146                 temp->name = "/dev/null";
 147                 strcpy(temp->hex, ".");
 148                 strcpy(temp->mode, ".");
 149                 return;
 150         }
 151
 152         if (one->sha1_valid &&
 153             !memcmp(one->u.sha1, null_sha1, sizeof(null_sha1))) {
 154                 one->sha1_valid = 0;
 155                 one->u.name = name;
 156         }
 157
 158         if (!one->sha1_valid) {
 159                 struct stat st;
 160                 temp->name = one->u.name;
 161                 if (stat(temp->name, &st) < 0) {
 162                         if (errno == ENOENT)
 163                                 goto not_a_valid_file;
 164                         die("stat(%s): %s", temp->name, strerror(errno));
 165                 }
 166                 strcpy(temp->hex, sha1_to_hex(null_sha1));
 167                 sprintf(temp->mode, "%06o",
 168                         S_IFREG |ce_permissions(st.st_mode));
 169         }
 170         else {
 171                 int fd;
 172                 void *blob;
 173                 char type[20];
 174                 unsigned long size;
 175
 176                 blob = read_sha1_file(one->u.sha1, type, &size);
 177                 if (!blob || strcmp(type, "blob"))
 178                         die("unable to read blob object for %s (%s)",
 179                             name, sha1_to_hex(one->u.sha1));
 180
 181                 strcpy(temp->tmp_path, ".diff_XXXXXX");
 182                 fd = mkstemp(temp->tmp_path);
 183                 if (fd < 0)
 184                         die("unable to create temp-file");
 185                 if (write(fd, blob, size) != size)
 186                         die("unable to write temp-file");
 187                 close(fd);
 188                 free(blob);
 189                 temp->name = temp->tmp_path;
 190                 strcpy(temp->hex, sha1_to_hex(one->u.sha1));
 191                 temp->hex[40] = 0;
 192                 sprintf(temp->mode, "%06o", one->mode);
 193         }
 194 }
 195
 196 static void remove_tempfile(void)
 197 {
 198         int i;
 199
 200         for (i = 0; i < 2; i++)
 201                 if (diff_temp[i].name == diff_temp[i].tmp_path) {
 202                         unlink(diff_temp[i].name);
 203                         diff_temp[i].name = NULL;
 204                 }
 205 }
 206
 207 static void remove_tempfile_on_signal(int signo)
 208 {
 209         remove_tempfile();
 210 }
 211
 212 /* An external diff command takes:
 213  *
 214  * diff-cmd name infile1 infile1-sha1 infile1-mode \
 215  *               infile2 infile2-sha1 infile2-mode.
 216  *
 217  */
 218 void run_external_diff(const char *name,
 219                        struct diff_spec *one,
 220                        struct diff_spec *two)
 221 {
 222         struct diff_tempfile *temp = diff_temp;
 223         pid_t pid;
 224         int status;
 225         static int atexit_asked = 0;
 226
 227         if (one && two) {
 228                 prepare_temp_file(name, &temp[0], one);
 229                 prepare_temp_file(name, &temp[1], two);
 230                 if (! atexit_asked &&
 231                     (temp[0].name == temp[0].tmp_path ||
 232                      temp[1].name == temp[1].tmp_path)) {
 233                         atexit_asked = 1;
 234                         atexit(remove_tempfile);
 235                 }
 236                 signal(SIGINT, remove_tempfile_on_signal);
 237         }
 238
 239         fflush(NULL);
 240         pid = fork();
 241         if (pid < 0)
 242                 die("unable to fork");
 243         if (!pid) {
 244                 const char *pgm = external_diff();
 245                 if (pgm) {
 246                         if (one && two)
 247                                 execlp(pgm, pgm,
 248                                        name,
 249                                        temp[0].name, temp[0].hex, temp[0].mode,
 250                                        temp[1].name, temp[1].hex, temp[1].mode,
 251                                        NULL);
 252                         else
 253                                 execlp(pgm, pgm, name, NULL);
 254                 }
 255                 /*
 256                  * otherwise we use the built-in one.
 257                  */
 258                 if (one && two)
 259                         builtin_diff(name, temp);
 260                 else
 261                         printf("* Unmerged path %s\n", name);
 262                 exit(0);
 263         }
 264         if (waitpid(pid, &status, 0) < 0 ||
 265             !WIFEXITED(status) || WEXITSTATUS(status)) {
 266                 /* Earlier we did not check the exit status because
 267                  * diff exits non-zero if files are different, and
 268                  * we are not interested in knowing that.  It was a
 269                  * mistake which made it harder to quit a diff-*
 270                  * session that uses the git-apply-patch-script as
 271                  * the GIT_EXTERNAL_DIFF.  A custom GIT_EXTERNAL_DIFF
 272                  * should also exit non-zero only when it wants to
 273                  * abort the entire diff-* session.
 274                  */
 275                 remove_tempfile();
 276                 fprintf(stderr, "external diff died, stopping at %s.\n", name);
 277                 exit(1);
 278         }
 279         remove_tempfile();
 280 }
 281
 282 void diff_addremove(int addremove, unsigned mode,
 283                     const unsigned char *sha1,
 284                     const char *base, const char *path)
 285 {
 286         char concatpath[PATH_MAX];
 287         struct diff_spec spec[2], *one, *two;
 288
 289         memcpy(spec[0].u.sha1, sha1, 20);
 290         spec[0].mode = mode;
 291         spec[0].sha1_valid = spec[0].file_valid = 1;
 292         spec[1].file_valid = 0;
 293
 294         if (addremove == '+') {
 295                 one = spec + 1; two = spec;
 296         } else {
 297                 one = spec; two = one + 1;
 298         }
 299
 300         if (path) {
 301                 strcpy(concatpath, base);
 302                 strcat(concatpath, path);
 303         }
 304         run_external_diff(path ? concatpath : base, one, two);
 305 }
 306
 307 void diff_change(unsigned old_mode, unsigned new_mode,
 308                  const unsigned char *old_sha1,
 309                  const unsigned char *new_sha1,
 310                  const char *base, const char *path) {
 311         char concatpath[PATH_MAX];
 312         struct diff_spec spec[2];
 313
 314         memcpy(spec[0].u.sha1, old_sha1, 20);
 315         spec[0].mode = old_mode;
 316         memcpy(spec[1].u.sha1, new_sha1, 20);
 317         spec[1].mode = new_mode;
 318         spec[0].sha1_valid = spec[0].file_valid = 1;
 319         spec[1].sha1_valid = spec[1].file_valid = 1;
 320
 321         if (path) {
 322                 strcpy(concatpath, base);
 323                 strcat(concatpath, path);
 324         }
 325         run_external_diff(path ? concatpath : base, &spec[0], &spec[1]);
 326 }
 327
 328 void diff_unmerge(const char *path)
 329 {
 330         run_external_diff(path, NULL, NULL);
 331 }