使用 Git Grep 进行搜索
用 git grep 命令查找 Git 库里面的某段文字是很方便的。当然，你也可以用 Unix 下的grep命令进行搜索，但是git grep命令能让你不用签出(checkout)历史文件，就能查找它们。
例如，你要看git.git这个仓库里每个使用xmmap函数的地方，你可以运行下面的命令：
$ git grep xmmap
config.c: contents = xmmap(NULL, contents_sz, PROT_READ,
diff.c: s->data = xmmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
git-compat-util.h:extern void *xmmap(void *start, size_t length, int prot, int fla
read-cache.c: mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
refs.c: log_mapped = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, logfd, 0);
sha1_file.c: map = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, fd, 0);
sha1_file.c: idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd, 0);
sha1_file.c: win->base = xmmap(NULL, win->len,
sha1_file.c: map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, f
sha1_file.c: buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
wrapper.c:void *xmmap(void *start, size_t length,如果你要显示行号，你可以添加-n选项：
$>git grep -n xmmap
config.c:1016: contents = xmmap(NULL, contents_sz, PROT_READ,
diff.c:1833: s->data = xmmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd,
git-compat-util.h:291:extern void *xmmap(void *start, size_t length, int prot, int
read-cache.c:1178: mmap = xmmap(NULL, mmap_size, PROT_READ | PROT_WRITE, MAP_
refs.c:1345: log_mapped = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, logfd, 0);
sha1_file.c:377: map = xmmap(NULL, mapsz, PROT_READ, MAP_PRIVATE, fd, 0);
sha1_file.c:479: idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd
sha1_file.c:780: win->base = xmmap(NULL, win->len,
sha1_file.c:1076: map = xmmap(NULL, *size, PROT_READ, MAP_PR
sha1_file.c:2393: buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd
wrapper.c:89:void *xmmap(void *start, size_t length,如果我们想只显示文件名，我们可以使用--name-onley选项：
$>git grep --name-only xmmap
config.c
diff.c
git-compat-util.h
read-cache.c
refs.c
sha1_file.c
wrapper.c我们可以用-c选项，可以查看每个文件里有多少行匹配内容(line matches)：
$>git grep -c xmmap
config.c:1
diff.c:1
git-compat-util.h:1
read-cache.c:1
refs.c:1
sha1_file.c:5
wrapper.c:1现在，如果我们要查找 Git 仓库里某个特定版本里的内容，我们可以像下面一样在命令行末尾加上标签名(tag reference)：
$ git grep xmmap v1.5.0
v1.5.0:config.c: contents = xmmap(NULL, st.st_size, PROT_READ,
v1.5.0:diff.c: s->data = xmmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd,
v1.5.0:git-compat-util.h:static inline void *xmmap(void *start, size_t length,
v1.5.0:read-cache.c: cache_mmap = xmmap(NULL, cache_mmap_size,
v1.5.0:refs.c: log_mapped = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, logfd
v1.5.0:sha1_file.c: map = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd,
v1.5.0:sha1_file.c: idx_map = xmmap(NULL, idx_size, PROT_READ, MAP_PRIVATE, fd
v1.5.0:sha1_file.c: win->base = xmmap(NULL, win->len,
v1.5.0:sha1_file.c: map = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd,
v1.5.0:sha1_file.c: buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd我可以看到‘1.5.0 版’和当前版本间一些区别：在‘1.5.0 版’中，xmmap 没有在 wrapper.c 中出现。
我们也可以组合一些搜索条件，下面的命令就是查找我们在仓库的哪个地方定义了‘SORT_DIRENT’。
$ git grep -e '#define' --and -e SORT_DIRENT
builtin-fsck.c:#define SORT_DIRENT 0
builtin-fsck.c:#define SORT_DIRENT 1我不但可以进行‘与’(both)条件搜索操作，也可以进行‘或’(either)条件搜索操作。
$ git grep --all-match -e '#define' -e SORT_DIRENT
builtin-fsck.c:#define REACHABLE 0x0001
builtin-fsck.c:#define SEEN 0x0002
builtin-fsck.c:#define ERROR_OBJECT 01
builtin-fsck.c:#define ERROR_REACHABLE 02
builtin-fsck.c:#define SORT_DIRENT 0
builtin-fsck.c:#define DIRENT_SORT_HINT(de) 0
builtin-fsck.c:#define SORT_DIRENT 1
builtin-fsck.c:#define DIRENT_SORT_HINT(de) ((de)->d_ino)
builtin-fsck.c:#define MAX_SHA1_ENTRIES (1024)
builtin-fsck.c: if (SORT_DIRENT)我们也可以查找出符合一个条件(term)且符合两个条件(terms)之一的文件行。例如我们要找出名字中含有‘PATH’或是‘MAX’的常量定义：
$ git grep -e '#define' --and \( -e PATH -e MAX \)
abspath.c:#define MAXDEPTH 5
builtin-blame.c:#define MORE_THAN_ONE_PATH (1u<<13)
builtin-blame.c:#define MAXSG 16
builtin-describe.c:#define MAX_TAGS (FLAG_BITS - 1)
builtin-fetch-pack.c:#define MAX_IN_VAIN 256
builtin-fsck.c:#define MAX_SHA1_ENTRIES (1024)
...译者注：就是‘与’条件搜索和‘或’条件搜索可以组合使用。
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