git/git.c
Andreas Ericsson 8e49d50388 C implementation of the 'git' program, take two.
This patch provides a C implementation of the 'git' program and
introduces support for putting the git-* commands in a directory
of their own. It also saves some time on executing those commands
in a tight loop and it prints the currently available git commands
in a nicely formatted list.

The location of the GIT_EXEC_PATH (name discussion's closed, thank gods)
can be obtained by running

	git --exec-path

which will hopefully give porcelainistas ample time to adapt their
heavy-duty loops to call the core programs directly and thus save
the extra fork() / execve() overhead, although that's not really
necessary any more.

The --exec-path value is prepended to $PATH, so the git-* programs
should Just Work without ever requiring any changes to how they call
other programs in the suite.

Some timing values for 10000 invocations of git-var >&/dev/null:
	git.sh: 24.194s
	git.c:   9.044s
	git-var: 7.377s

The git-<tab><tab> behaviour can, along with the someday-to-be-deprecated
git-<command> form of invocation, be indefinitely retained by adding
the following line to one's .bash_profile or equivalent:

	PATH=$PATH:$(git --exec-path)

Experimental libraries can be used by either setting the environment variable
GIT_EXEC_PATH, or by using

	git --exec-path=/some/experimental/exec-path

Relative paths are properly grok'ed as exec-path values.

Signed-off-by: Andreas Ericsson <ae@op5.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>
2005-11-15 16:02:57 -08:00

230 lines
4.6 KiB
C

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <glob.h>
#ifndef PATH_MAX
# define PATH_MAX 4096
#endif
static const char git_usage[] =
"Usage: git [--version] [--exec-path[=GIT_EXEC_PATH]] [--help] COMMAND [ ARGS ]";
struct string_list {
size_t len;
char *str;
struct string_list *next;
};
/* most gui terms set COLUMNS (although some don't export it) */
static int term_columns(void)
{
char *col_string = getenv("COLUMNS");
int n_cols = 0;
if (col_string && (n_cols = atoi(col_string)) > 0)
return n_cols;
return 80;
}
static inline void mput_char(char c, unsigned int num)
{
while(num--)
putchar(c);
}
static void pretty_print_string_list(struct string_list *list, int longest)
{
int cols = 1;
int space = longest + 1; /* min 1 SP between words */
int max_cols = term_columns() - 1; /* don't print *on* the edge */
if (space < max_cols)
cols = max_cols / space;
while (list) {
int c;
printf(" ");
for (c = cols; c && list; list = list->next) {
printf("%s", list->str);
if (--c)
mput_char(' ', space - list->len);
}
putchar('\n');
}
}
static void list_commands(const char *exec_path, const char *pattern)
{
struct string_list *list = NULL, *tail = NULL;
unsigned int longest = 0, i;
glob_t gl;
if (chdir(exec_path) < 0) {
printf("git: '%s': %s\n", exec_path, strerror(errno));
exit(1);
}
i = glob(pattern, 0, NULL, &gl);
switch(i) {
case GLOB_NOSPACE:
puts("Out of memory when running glob()");
exit(2);
case GLOB_ABORTED:
printf("'%s': Read error: %s\n", exec_path, strerror(errno));
exit(2);
case GLOB_NOMATCH:
printf("No git commands available in '%s'.\n", exec_path);
printf("Do you need to specify --exec-path or set GIT_EXEC_PATH?\n");
exit(1);
}
for (i = 0; i < gl.gl_pathc; i++) {
int len = strlen(gl.gl_pathv[i] + 4);
if (access(gl.gl_pathv[i], X_OK))
continue;
if (longest < len)
longest = len;
if (!tail)
tail = list = malloc(sizeof(struct string_list));
else {
tail->next = malloc(sizeof(struct string_list));
tail = tail->next;
}
tail->len = len;
tail->str = gl.gl_pathv[i] + 4;
tail->next = NULL;
}
printf("git commands available in '%s'\n", exec_path);
printf("----------------------------");
mput_char('-', strlen(exec_path));
putchar('\n');
pretty_print_string_list(list, longest);
putchar('\n');
}
#ifdef __GNUC__
static void usage(const char *exec_path, const char *fmt, ...)
__attribute__((__format__(__printf__, 2, 3), __noreturn__));
#endif
static void usage(const char *exec_path, const char *fmt, ...)
{
if (fmt) {
va_list ap;
va_start(ap, fmt);
printf("git: ");
vprintf(fmt, ap);
va_end(ap);
putchar('\n');
}
else
puts(git_usage);
putchar('\n');
if(exec_path)
list_commands(exec_path, "git-*");
exit(1);
}
static void prepend_to_path(const char *dir, int len)
{
char *path, *old_path = getenv("PATH");
int path_len = len;
if (!old_path)
old_path = "/bin:/usr/bin:.";
path_len = len + strlen(old_path) + 1;
path = malloc(path_len + 1);
path[path_len + 1] = '\0';
memcpy(path, dir, len);
path[len] = ':';
memcpy(path + len + 1, old_path, path_len - len);
setenv("PATH", path, 1);
}
int main(int argc, char **argv, char **envp)
{
char git_command[PATH_MAX + 1];
char wd[PATH_MAX + 1];
int i, len, show_help = 0;
char *exec_path = getenv("GIT_EXEC_PATH");
getcwd(wd, PATH_MAX);
if (!exec_path)
exec_path = GIT_EXEC_PATH;
for (i = 1; i < argc; i++) {
char *arg = argv[i];
if (strncmp(arg, "--", 2))
break;
arg += 2;
if (!strncmp(arg, "exec-path", 9)) {
arg += 9;
if (*arg == '=')
exec_path = arg + 1;
else {
puts(exec_path);
exit(0);
}
}
else if (!strcmp(arg, "version")) {
printf("git version %s\n", GIT_VERSION);
exit(0);
}
else if (!strcmp(arg, "help"))
show_help = 1;
else if (!show_help)
usage(NULL, NULL);
}
if (i >= argc || show_help)
usage(exec_path, NULL);
/* allow relative paths, but run with exact */
if (chdir(exec_path)) {
printf("git: '%s': %s\n", exec_path, strerror(errno));
exit (1);
}
getcwd(git_command, sizeof(git_command));
chdir(wd);
len = strlen(git_command);
prepend_to_path(git_command, len);
strncat(&git_command[len], "/git-", sizeof(git_command) - len);
len += 5;
strncat(&git_command[len], argv[i], sizeof(git_command) - len);
if (access(git_command, X_OK))
usage(exec_path, "'%s' is not a git-command", argv[i]);
/* execve() can only ever return if it fails */
execve(git_command, &argv[i], envp);
printf("Failed to run command '%s': %s\n", git_command, strerror(errno));
return 1;
}