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_opts = "-pu";
  10
  11 static const char *external_diff(void)
  12 {
  13         static char *external_diff_cmd = NULL;
  14         static int done_preparing = 0;
  15
  16         if (done_preparing)
  17                 return external_diff_cmd;
  18
  19         /*
  20          * Default values above are meant to match the
  21          * Linux kernel development style.  Examples of
  22          * alternative styles you can specify via environment
  23          * variables are:
  24          *
  25          * GIT_DIFF_OPTS="-c";
  26          */
  27         if (getenv("GIT_EXTERNAL_DIFF"))
  28                 external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
  29
  30         /* In case external diff fails... */
  31         diff_opts = getenv("GIT_DIFF_OPTS") ? : diff_opts;
  32
  33         done_preparing = 1;
  34         return external_diff_cmd;
  35 }
  36
  37 /* Help to copy the thing properly quoted for the shell safety.
  38  * any single quote is replaced with '\'', and the caller is
  39  * expected to enclose the result within a single quote pair.
  40  *
  41  * E.g.
  42  *  original     sq_expand     result
  43  *  name     ==> name      ==> 'name'
  44  *  a b      ==> a b       ==> 'a b'
  45  *  a'b      ==> a'\''b    ==> 'a'\''b'
  46  */
  47 static char *sq_expand(const char *src)
  48 {
  49         static char *buf = NULL;
  50         int cnt, c;
  51         const char *cp;
  52         char *bp;
  53
  54         /* count bytes needed to store the quoted string. */
  55         for (cnt = 1, cp = src; *cp; cnt++, cp++)
  56                 if (*cp == '\'')
  57                         cnt += 3;
  58
  59         buf = xmalloc(cnt);
  60         bp = buf;
  61         while ((c = *src++)) {
  62                 if (c != '\'')
  63                         *bp++ = c;
  64                 else {
  65                         bp = strcpy(bp, "'\\''");
  66                         bp += 4;
  67                 }
  68         }
  69         *bp = 0;
  70         return buf;
  71 }
  72
  73 static struct diff_tempfile {
  74         const char *name;
  75         char hex[41];
  76         char mode[10];
  77         char tmp_path[50];
  78 } diff_temp[2];
  79
  80 static void builtin_diff(const char *name,
  81                          struct diff_tempfile *temp)
  82 {
  83         int i, next_at;
  84         const char *diff_cmd = "diff -L'%s%s%s' -L'%s%s%s'";
  85         const char *diff_arg  = "'%s' '%s'";
  86         const char *input_name_sq[2];
  87         const char *path0[2];
  88         const char *path1[2];
  89         char mode[2][20];
  90         const char *name_sq = sq_expand(name);
  91         char *cmd;
  92
  93         /* diff_cmd and diff_arg have 8 %s in total which makes
  94          * the sum of these strings 16 bytes larger than required.
  95          * we use 2 spaces around diff-opts, and we need to count
  96          * terminating NUL, so we subtract 13 here.
  97          */
  98         int cmd_size = (strlen(diff_cmd) + strlen(diff_opts) +
  99                         strlen(diff_arg) - 13);
 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                         mode[i][0] = 0;
 106                 } else {
 107                         path0[i] = i ? "l/" : "k/";
 108                         path1[i] = name_sq;
 109                         sprintf(mode[i], "  (mode:%s)", temp[i].mode);
 110                 }
 111                 cmd_size += (strlen(path0[i]) + strlen(path1[i]) +
 112                              strlen(mode[i]) + strlen(input_name_sq[i]));
 113         }
 114
 115         cmd = xmalloc(cmd_size);
 116
 117         next_at = 0;
 118         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 119                             diff_cmd,
 120                             path0[0], path1[0], mode[0],
 121                             path0[1], path1[1], mode[1]);
 122         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 123                             " %s ", diff_opts);
 124         next_at += snprintf(cmd+next_at, cmd_size-next_at,
 125                             diff_arg, input_name_sq[0], input_name_sq[1]);
 126
 127         execlp("/bin/sh","sh", "-c", cmd, NULL);
 128 }
 129
 130 static void prepare_temp_file(const char *name,
 131                               struct diff_tempfile *temp,
 132                               struct diff_spec *one)
 133 {
 134         static unsigned char null_sha1[20] = { 0, };
 135
 136         if (!one->file_valid) {
 137         not_a_valid_file:
 138                 temp->name = "/dev/null";
 139                 strcpy(temp->hex, ".");
 140                 strcpy(temp->mode, ".");
 141                 return;
 142         }
 143
 144         if (one->sha1_valid &&
 145             !memcmp(one->u.sha1, null_sha1, sizeof(null_sha1))) {
 146                 one->sha1_valid = 0;
 147                 one->u.name = name;
 148         }
 149
 150         if (!one->sha1_valid) {
 151                 struct stat st;
 152                 temp->name = one->u.name;
 153                 if (stat(temp->name, &st) < 0) {
 154                         if (errno == ENOENT)
 155                                 goto not_a_valid_file;
 156                         die("stat(%s): %s", temp->name, strerror(errno));
 157                 }
 158                 strcpy(temp->hex, ".");
 159                 sprintf(temp->mode, "%06o",
 160                         S_IFREG |ce_permissions(st.st_mode));
 161         }
 162         else {
 163                 int fd;
 164                 void *blob;
 165                 char type[20];
 166                 unsigned long size;
 167
 168                 blob = read_sha1_file(one->u.sha1, type, &size);
 169                 if (!blob || strcmp(type, "blob"))
 170                         die("unable to read blob object for %s (%s)",
 171                             name, sha1_to_hex(one->u.sha1));
 172
 173                 strcpy(temp->tmp_path, ".diff_XXXXXX");
 174                 fd = mkstemp(temp->tmp_path);
 175                 if (fd < 0)
 176                         die("unable to create temp-file");
 177                 if (write(fd, blob, size) != size)
 178                         die("unable to write temp-file");
 179                 close(fd);
 180                 free(blob);
 181                 temp->name = temp->tmp_path;
 182                 strcpy(temp->hex, sha1_to_hex(one->u.sha1));
 183                 temp->hex[40] = 0;
 184                 sprintf(temp->mode, "%06o", one->mode);
 185         }
 186 }
 187
 188 static void remove_tempfile(void)
 189 {
 190         int i;
 191
 192         for (i = 0; i < 2; i++)
 193                 if (diff_temp[i].name == diff_temp[i].tmp_path) {
 194                         unlink(diff_temp[i].name);
 195                         diff_temp[i].name = NULL;
 196                 }
 197 }
 198
 199 /* An external diff command takes:
 200  *
 201  * diff-cmd name infile1 infile1-sha1 infile1-mode \
 202  *               infile2 infile2-sha1 infile2-mode.
 203  *
 204  */
 205 void run_external_diff(const char *name,
 206                        struct diff_spec *one,
 207                        struct diff_spec *two)
 208 {
 209         struct diff_tempfile *temp = diff_temp;
 210         int pid, status;
 211         static int atexit_asked = 0;
 212
 213         if (one && two) {
 214                 prepare_temp_file(name, &temp[0], one);
 215                 prepare_temp_file(name, &temp[1], two);
 216                 if (! atexit_asked &&
 217                     (temp[0].name == temp[0].tmp_path ||
 218                      temp[1].name == temp[1].tmp_path)) {
 219                         atexit_asked = 1;
 220                         atexit(remove_tempfile);
 221                 }
 222         }
 223
 224         fflush(NULL);
 225         pid = fork();
 226         if (pid < 0)
 227                 die("unable to fork");
 228         if (!pid) {
 229                 const char *pgm = external_diff();
 230                 if (pgm) {
 231                         if (one && two)
 232                                 execlp(pgm, pgm,
 233                                        name,
 234                                        temp[0].name, temp[0].hex, temp[0].mode,
 235                                        temp[1].name, temp[1].hex, temp[1].mode,
 236                                        NULL);
 237                         else
 238                                 execlp(pgm, pgm, name, NULL);
 239                 }
 240                 /*
 241                  * otherwise we use the built-in one.
 242                  */
 243                 if (one && two)
 244                         builtin_diff(name, temp);
 245                 else
 246                         printf("* Unmerged path %s\n", name);
 247                 exit(0);
 248         }
 249         if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status))
 250                 die("diff program failed");
 251
 252         remove_tempfile();
 253 }
 254
 255 void diff_addremove(int addremove, unsigned mode,
 256                     const unsigned char *sha1,
 257                     const char *base, const char *path)
 258 {
 259         char concatpath[PATH_MAX];
 260         struct diff_spec spec[2], *one, *two;
 261
 262         memcpy(spec[0].u.sha1, sha1, 20);
 263         spec[0].mode = mode;
 264         spec[0].sha1_valid = spec[0].file_valid = 1;
 265         spec[1].file_valid = 0;
 266
 267         if (addremove == '+') {
 268                 one = spec + 1; two = spec;
 269         } else {
 270                 one = spec; two = one + 1;
 271         }
 272
 273         if (path) {
 274                 strcpy(concatpath, base);
 275                 strcat(concatpath, path);
 276         }
 277         run_external_diff(path ? concatpath : base, one, two);
 278 }
 279
 280 void diff_change(unsigned old_mode, unsigned new_mode,
 281                  const unsigned char *old_sha1,
 282                  const unsigned char *new_sha1,
 283                  const char *base, const char *path) {
 284         char concatpath[PATH_MAX];
 285         struct diff_spec spec[2];
 286
 287         memcpy(spec[0].u.sha1, old_sha1, 20);
 288         spec[0].mode = old_mode;
 289         memcpy(spec[1].u.sha1, new_sha1, 20);
 290         spec[1].mode = new_mode;
 291         spec[0].sha1_valid = spec[0].file_valid = 1;
 292         spec[1].sha1_valid = spec[1].file_valid = 1;
 293
 294         if (path) {
 295                 strcpy(concatpath, base);
 296                 strcat(concatpath, path);
 297         }
 298         run_external_diff(path ? concatpath : base, &spec[0], &spec[1]);
 299 }
 300
 301 void diff_unmerge(const char *path)
 302 {
 303         run_external_diff(path, NULL, NULL);
 304 }