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authorJunio C Hamano <junkio@cox.net>2007-01-02 07:31:08 (GMT)
committerJunio C Hamano <junkio@cox.net>2007-01-08 11:02:11 (GMT)
commitc847f537125ceab3425205721fdaaa834e6d8a83 (patch)
treeff9d242fe9d7bd4008f16d7f43e860e0db861981
parent0016a48251abefed11efc919703d980a21c95f2c (diff)
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Detached HEAD (experimental)
This allows "git checkout v1.4.3" to dissociate the HEAD of repository from any branch. After this point, "git branch" starts reporting that you are not on any branch. You can go back to an existing branch by saying "git checkout master", for example. This is still experimental. While I think it makes sense to allow commits on top of detached HEAD, it is rather dangerous unless you are careful in the current form. Next "git checkout master" will obviously lose what you have done, so we might want to require "git checkout -f" out of a detached HEAD if we find that the HEAD commit is not an ancestor of any other branches. There is no such safety valve implemented right now. On the other hand, the reason the user did not start the ad-hoc work on a new branch with "git checkout -b" was probably because the work was of a throw-away nature, so the convenience of not having that safety valve might be even better. The user, after accumulating some commits on top of a detached HEAD, can always create a new branch with "git checkout -b" not to lose useful work done while the HEAD was detached. We'll see. Signed-off-by: Junio C Hamano <junkio@cox.net>
-rw-r--r--builtin-branch.c24
-rw-r--r--cache.h2
-rwxr-xr-xgit-checkout.sh16
-rw-r--r--path.c26
-rw-r--r--setup.c5
5 files changed, 50 insertions, 23 deletions
diff --git a/builtin-branch.c b/builtin-branch.c
index 487965b..c760e18 100644
--- a/builtin-branch.c
+++ b/builtin-branch.c
@@ -308,7 +308,8 @@ static void print_ref_list(int kinds, int detached, int verbose, int abbrev)
free_ref_list(&ref_list);
}
-static void create_branch(const char *name, const char *start,
+static void create_branch(const char *name, const char *start_name,
+ unsigned char *start_sha1,
int force, int reflog)
{
struct ref_lock *lock;
@@ -327,9 +328,14 @@ static void create_branch(const char *name, const char *start,
die("Cannot force update the current branch.");
}
- if (get_sha1(start, sha1) ||
- (commit = lookup_commit_reference(sha1)) == NULL)
- die("Not a valid branch point: '%s'.", start);
+ if (start_sha1)
+ /* detached HEAD */
+ hashcpy(sha1, start_sha1);
+ else if (get_sha1(start_name, sha1))
+ die("Not a valid object name: '%s'.", start_name);
+
+ if ((commit = lookup_commit_reference(sha1)) == NULL)
+ die("Not a valid branch point: '%s'.", start_name);
hashcpy(sha1, commit->object.sha1);
lock = lock_any_ref_for_update(ref, NULL);
@@ -338,7 +344,8 @@ static void create_branch(const char *name, const char *start,
if (reflog) {
log_all_ref_updates = 1;
- snprintf(msg, sizeof msg, "branch: Created from %s", start);
+ snprintf(msg, sizeof msg, "branch: Created from %s",
+ start_name);
}
if (write_ref_sha1(lock, sha1, msg) < 0)
@@ -350,6 +357,9 @@ static void rename_branch(const char *oldname, const char *newname, int force)
char oldref[PATH_MAX], newref[PATH_MAX], logmsg[PATH_MAX*2 + 100];
unsigned char sha1[20];
+ if (!oldname)
+ die("cannot rename the curren branch while not on any.");
+
if (snprintf(oldref, sizeof(oldref), "refs/heads/%s", oldname) > sizeof(oldref))
die("Old branchname too long");
@@ -474,9 +484,9 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
else if (rename && (i == argc - 2))
rename_branch(argv[i], argv[i + 1], force_rename);
else if (i == argc - 1)
- create_branch(argv[i], head, force_create, reflog);
+ create_branch(argv[i], head, head_sha1, force_create, reflog);
else if (i == argc - 2)
- create_branch(argv[i], argv[i + 1], force_create, reflog);
+ create_branch(argv[i], argv[i+1], NULL, force_create, reflog);
else
usage(builtin_branch_usage);
diff --git a/cache.h b/cache.h
index 36be64e..5218548 100644
--- a/cache.h
+++ b/cache.h
@@ -299,7 +299,7 @@ extern char *sha1_to_hex(const unsigned char *sha1); /* static buffer result! */
extern int read_ref(const char *filename, unsigned char *sha1);
extern const char *resolve_ref(const char *path, unsigned char *sha1, int, int *);
extern int create_symref(const char *ref, const char *refs_heads_master);
-extern int validate_symref(const char *ref);
+extern int validate_headref(const char *ref);
extern int base_name_compare(const char *name1, int len1, int mode1, const char *name2, int len2, int mode2);
extern int cache_name_compare(const char *name1, int len1, const char *name2, int len2);
diff --git a/git-checkout.sh b/git-checkout.sh
index 92ec069..8e11ca4 100755
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -144,13 +144,19 @@ fi
# are switching to, then we'd better just be checking out
# what we already had
-[ -z "$branch$newbranch" ] &&
- [ "$new" != "$old" ] &&
- die "git checkout: provided reference cannot be checked out directly
-
- You need -b to associate a new branch with the wanted checkout. Example:
+if test -z "$branch$newbranch" && test "$new" != "$old"
+then
+ # NEEDSWORK: we would want to have this command here
+ # that allows us to detach the HEAD atomically.
+ # git update-ref --detach HEAD "$new"
+ rm -f "$GIT_DIR/HEAD"
+ echo "$new" >"$GIT_DIR/HEAD"
+ echo >&2 "WARNING: you are not on ANY branch anymore.
+If you meant to create a new branch from the commit, you need -b to
+associate a new branch with the wanted checkout. Example:
git checkout -b <new_branch_name> $arg
"
+fi
if [ "X$old" = X ]
then
diff --git a/path.c b/path.c
index 066f621..94ddd7e 100644
--- a/path.c
+++ b/path.c
@@ -90,10 +90,11 @@ int git_mkstemp(char *path, size_t len, const char *template)
}
-int validate_symref(const char *path)
+int validate_headref(const char *path)
{
struct stat st;
char *buf, buffer[256];
+ unsigned char sha1[20];
int len, fd;
if (lstat(path, &st) < 0)
@@ -119,14 +120,23 @@ int validate_symref(const char *path)
/*
* Is it a symbolic ref?
*/
- if (len < 4 || memcmp("ref:", buffer, 4))
+ if (len < 4)
return -1;
- buf = buffer + 4;
- len -= 4;
- while (len && isspace(*buf))
- buf++, len--;
- if (len >= 5 && !memcmp("refs/", buf, 5))
+ if (!memcmp("ref:", buffer, 4)) {
+ buf = buffer + 4;
+ len -= 4;
+ while (len && isspace(*buf))
+ buf++, len--;
+ if (len >= 5 && !memcmp("refs/", buf, 5))
+ return 0;
+ }
+
+ /*
+ * Is this a detached HEAD?
+ */
+ if (!get_sha1_hex(buffer, sha1))
return 0;
+
return -1;
}
@@ -241,7 +251,7 @@ char *enter_repo(char *path, int strict)
return NULL;
if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
- validate_symref("HEAD") == 0) {
+ validate_headref("HEAD") == 0) {
putenv("GIT_DIR=.");
check_repository_format();
return path;
diff --git a/setup.c b/setup.c
index 2ae57f7..cc97f9f 100644
--- a/setup.c
+++ b/setup.c
@@ -138,7 +138,8 @@ const char **get_pathspec(const char *prefix, const char **pathspec)
* GIT_OBJECT_DIRECTORY environment variable
* - a refs/ directory
* - either a HEAD symlink or a HEAD file that is formatted as
- * a proper "ref:".
+ * a proper "ref:", or a regular file HEAD that has a properly
+ * formatted sha1 object name.
*/
static int is_git_directory(const char *suspect)
{
@@ -161,7 +162,7 @@ static int is_git_directory(const char *suspect)
return 0;
strcpy(path + len, "/HEAD");
- if (validate_symref(path))
+ if (validate_headref(path))
return 0;
return 1;