Merge branch 'dt/refs-pseudo'
authorJunio C Hamano <gitster@pobox.com>
Tue, 25 Aug 2015 21:57:08 +0000 (14:57 -0700)
committerJunio C Hamano <gitster@pobox.com>
Tue, 25 Aug 2015 21:57:08 +0000 (14:57 -0700)
To prepare for allowing a different "ref" backend to be plugged in
to the system, update_ref()/delete_ref() have been taught about
ref-like things like MERGE_HEAD that are per-worktree (they will
always be written to the filesystem inside $GIT_DIR).

* dt/refs-pseudo:
  pseudoref: check return values from read_ref()
  sequencer: replace write_cherry_pick_head with update_ref
  bisect: use update_ref
  pseudorefs: create and use pseudoref update and delete functions
  refs: add ref_type function
  refs: introduce pseudoref and per-worktree ref concepts

Documentation/glossary-content.txt
bisect.c
refs.c
refs.h
sequencer.c

index ab18f4b..8c6478b 100644 (file)
@@ -411,6 +411,27 @@ exclude;;
        core Git. Porcelains expose more of a <<def_SCM,SCM>>
        interface than the <<def_plumbing,plumbing>>.
 
+[[def_per_worktree_ref]]per-worktree ref::
+       Refs that are per-<<def_working_tree,worktree>>, rather than
+       global.  This is presently only <<def_HEAD,HEAD>>, but might
+       later include other unusual refs.
+
+[[def_pseudoref]]pseudoref::
+       Pseudorefs are a class of files under `$GIT_DIR` which behave
+       like refs for the purposes of rev-parse, but which are treated
+       specially by git.  Pseudorefs both have names that are all-caps,
+       and always start with a line consisting of a
+       <<def_SHA1,SHA-1>> followed by whitespace.  So, HEAD is not a
+       pseudoref, because it is sometimes a symbolic ref.  They might
+       optionally contain some additional data.  `MERGE_HEAD` and
+       `CHERRY_PICK_HEAD` are examples.  Unlike
+       <<def_per_worktree_ref,per-worktree refs>>, these files cannot
+       be symbolic refs, and never have reflogs.  They also cannot be
+       updated through the normal ref update machinery.  Instead,
+       they are updated by directly writing to the files.  However,
+       they can be read as if they were refs, so `git rev-parse
+       MERGE_HEAD` will work.
+
 [[def_pull]]pull::
        Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
        <<def_merge,merge>> it.  See also linkgit:git-pull[1].
index f9da9d1..041a13d 100644 (file)
--- a/bisect.c
+++ b/bisect.c
@@ -19,7 +19,6 @@ static struct object_id *current_bad_oid;
 
 static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
-static const char *argv_update_ref[] = {"update-ref", "--no-deref", "BISECT_HEAD", NULL, NULL};
 
 static const char *term_bad;
 static const char *term_good;
@@ -678,34 +677,16 @@ static int is_expected_rev(const struct object_id *oid)
        return res;
 }
 
-static void mark_expected_rev(char *bisect_rev_hex)
-{
-       int len = strlen(bisect_rev_hex);
-       const char *filename = git_path("BISECT_EXPECTED_REV");
-       int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
-
-       if (fd < 0)
-               die_errno("could not create file '%s'", filename);
-
-       bisect_rev_hex[len] = '\n';
-       write_or_die(fd, bisect_rev_hex, len + 1);
-       bisect_rev_hex[len] = '\0';
-
-       if (close(fd) < 0)
-               die("closing file %s: %s", filename, strerror(errno));
-}
-
-static int bisect_checkout(char *bisect_rev_hex, int no_checkout)
+static int bisect_checkout(const unsigned char *bisect_rev, int no_checkout)
 {
+       char bisect_rev_hex[GIT_SHA1_HEXSZ + 1];
 
-       mark_expected_rev(bisect_rev_hex);
+       memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
+       update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
 
        argv_checkout[2] = bisect_rev_hex;
        if (no_checkout) {
-               argv_update_ref[3] = bisect_rev_hex;
-               if (run_command_v_opt(argv_update_ref, RUN_GIT_CMD))
-                       die("update-ref --no-deref HEAD failed on %s",
-                           bisect_rev_hex);
+               update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
        } else {
                int res;
                res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
@@ -807,7 +788,7 @@ static void check_merge_bases(int no_checkout)
                        handle_skipped_merge_base(mb);
                } else {
                        printf("Bisecting: a merge base must be tested\n");
-                       exit(bisect_checkout(sha1_to_hex(mb), no_checkout));
+                       exit(bisect_checkout(mb, no_checkout));
                }
        }
 
@@ -951,7 +932,6 @@ int bisect_next_all(const char *prefix, int no_checkout)
        struct commit_list *tried;
        int reaches = 0, all = 0, nr, steps;
        const unsigned char *bisect_rev;
-       char bisect_rev_hex[GIT_SHA1_HEXSZ + 1];
 
        read_bisect_terms(&term_bad, &term_good);
        if (read_bisect_refs())
@@ -989,11 +969,10 @@ int bisect_next_all(const char *prefix, int no_checkout)
        }
 
        bisect_rev = revs.commits->item->object.sha1;
-       memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
 
        if (!hashcmp(bisect_rev, current_bad_oid->hash)) {
                exit_if_skipped_commits(tried, current_bad_oid);
-               printf("%s is the first %s commit\n", bisect_rev_hex,
+               printf("%s is the first %s commit\n", sha1_to_hex(bisect_rev),
                        term_bad);
                show_diff_tree(prefix, revs.commits->item);
                /* This means the bisection process succeeded. */
@@ -1006,7 +985,7 @@ int bisect_next_all(const char *prefix, int no_checkout)
               "(roughly %d step%s)\n", nr, (nr == 1 ? "" : "s"),
               steps, (steps == 1 ? "" : "s"));
 
-       return bisect_checkout(bisect_rev_hex, no_checkout);
+       return bisect_checkout(bisect_rev, no_checkout);
 }
 
 static inline int log2i(int n)
diff --git a/refs.c b/refs.c
index 8358019..b0e0fe5 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -2854,12 +2854,117 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
        return 0;
 }
 
+static int is_per_worktree_ref(const char *refname)
+{
+       return !strcmp(refname, "HEAD");
+}
+
+static int is_pseudoref_syntax(const char *refname)
+{
+       const char *c;
+
+       for (c = refname; *c; c++) {
+               if (!isupper(*c) && *c != '-' && *c != '_')
+                       return 0;
+       }
+
+       return 1;
+}
+
+enum ref_type ref_type(const char *refname)
+{
+       if (is_per_worktree_ref(refname))
+               return REF_TYPE_PER_WORKTREE;
+       if (is_pseudoref_syntax(refname))
+               return REF_TYPE_PSEUDOREF;
+       return REF_TYPE_NORMAL;
+}
+
+static int write_pseudoref(const char *pseudoref, const unsigned char *sha1,
+                          const unsigned char *old_sha1, struct strbuf *err)
+{
+       const char *filename;
+       int fd;
+       static struct lock_file lock;
+       struct strbuf buf = STRBUF_INIT;
+       int ret = -1;
+
+       strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
+
+       filename = git_path("%s", pseudoref);
+       fd = hold_lock_file_for_update(&lock, filename, LOCK_DIE_ON_ERROR);
+       if (fd < 0) {
+               strbuf_addf(err, "Could not open '%s' for writing: %s",
+                           filename, strerror(errno));
+               return -1;
+       }
+
+       if (old_sha1) {
+               unsigned char actual_old_sha1[20];
+
+               if (read_ref(pseudoref, actual_old_sha1))
+                       die("could not read ref '%s'", pseudoref);
+               if (hashcmp(actual_old_sha1, old_sha1)) {
+                       strbuf_addf(err, "Unexpected sha1 when writing %s", pseudoref);
+                       rollback_lock_file(&lock);
+                       goto done;
+               }
+       }
+
+       if (write_in_full(fd, buf.buf, buf.len) != buf.len) {
+               strbuf_addf(err, "Could not write to '%s'", filename);
+               rollback_lock_file(&lock);
+               goto done;
+       }
+
+       commit_lock_file(&lock);
+       ret = 0;
+done:
+       strbuf_release(&buf);
+       return ret;
+}
+
+static int delete_pseudoref(const char *pseudoref, const unsigned char *old_sha1)
+{
+       static struct lock_file lock;
+       const char *filename;
+
+       filename = git_path("%s", pseudoref);
+
+       if (old_sha1 && !is_null_sha1(old_sha1)) {
+               int fd;
+               unsigned char actual_old_sha1[20];
+
+               fd = hold_lock_file_for_update(&lock, filename,
+                                              LOCK_DIE_ON_ERROR);
+               if (fd < 0)
+                       die_errno(_("Could not open '%s' for writing"), filename);
+               if (read_ref(pseudoref, actual_old_sha1))
+                       die("could not read ref '%s'", pseudoref);
+               if (hashcmp(actual_old_sha1, old_sha1)) {
+                       warning("Unexpected sha1 when deleting %s", pseudoref);
+                       rollback_lock_file(&lock);
+                       return -1;
+               }
+
+               unlink(filename);
+               rollback_lock_file(&lock);
+       } else {
+               unlink(filename);
+       }
+
+       return 0;
+}
+
 int delete_ref(const char *refname, const unsigned char *old_sha1,
               unsigned int flags)
 {
        struct ref_transaction *transaction;
        struct strbuf err = STRBUF_INIT;
 
+       if (ref_type(refname) == REF_TYPE_PSEUDOREF)
+               return delete_pseudoref(refname, old_sha1);
+
        transaction = ref_transaction_begin(&err);
        if (!transaction ||
            ref_transaction_delete(transaction, refname, old_sha1,
@@ -3961,17 +4066,25 @@ int update_ref(const char *msg, const char *refname,
               const unsigned char *new_sha1, const unsigned char *old_sha1,
               unsigned int flags, enum action_on_err onerr)
 {
-       struct ref_transaction *t;
+       struct ref_transaction *t = NULL;
        struct strbuf err = STRBUF_INIT;
+       int ret = 0;
 
-       t = ref_transaction_begin(&err);
-       if (!t ||
-           ref_transaction_update(t, refname, new_sha1, old_sha1,
-                                  flags, msg, &err) ||
-           ref_transaction_commit(t, &err)) {
+       if (ref_type(refname) == REF_TYPE_PSEUDOREF) {
+               ret = write_pseudoref(refname, new_sha1, old_sha1, &err);
+       } else {
+               t = ref_transaction_begin(&err);
+               if (!t ||
+                   ref_transaction_update(t, refname, new_sha1, old_sha1,
+                                          flags, msg, &err) ||
+                   ref_transaction_commit(t, &err)) {
+                       ret = 1;
+                       ref_transaction_free(t);
+               }
+       }
+       if (ret) {
                const char *str = "update_ref failed for ref '%s': %s";
 
-               ref_transaction_free(t);
                switch (onerr) {
                case UPDATE_REFS_MSG_ON_ERR:
                        error(str, refname, err.buf);
@@ -3986,7 +4099,8 @@ int update_ref(const char *msg, const char *refname,
                return 1;
        }
        strbuf_release(&err);
-       ref_transaction_free(t);
+       if (t)
+               ref_transaction_free(t);
        return 0;
 }
 
diff --git a/refs.h b/refs.h
index 6a3fa6d..e9a5f32 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -445,6 +445,14 @@ extern int parse_hide_refs_config(const char *var, const char *value, const char
 
 extern int ref_is_hidden(const char *);
 
+enum ref_type {
+       REF_TYPE_PER_WORKTREE,
+       REF_TYPE_PSEUDOREF,
+       REF_TYPE_NORMAL,
+};
+
+enum ref_type ref_type(const char *refname);
+
 enum expire_reflog_flags {
        EXPIRE_REFLOGS_DRY_RUN = 1 << 0,
        EXPIRE_REFLOGS_UPDATE_REF = 1 << 1,
index 147adfa..a0600ae 100644 (file)
@@ -163,23 +163,6 @@ static void free_message(struct commit *commit, struct commit_message *msg)
        unuse_commit_buffer(commit, msg->message);
 }
 
-static void write_cherry_pick_head(struct commit *commit, const char *pseudoref)
-{
-       const char *filename;
-       int fd;
-       struct strbuf buf = STRBUF_INIT;
-
-       strbuf_addf(&buf, "%s\n", sha1_to_hex(commit->object.sha1));
-
-       filename = git_path("%s", pseudoref);
-       fd = open(filename, O_WRONLY | O_CREAT, 0666);
-       if (fd < 0)
-               die_errno(_("Could not open '%s' for writing"), filename);
-       if (write_in_full(fd, buf.buf, buf.len) != buf.len || close(fd))
-               die_errno(_("Could not write to '%s'"), filename);
-       strbuf_release(&buf);
-}
-
 static void print_advice(int show_hint, struct replay_opts *opts)
 {
        char *msg = getenv("GIT_CHERRY_PICK_HELP");
@@ -609,9 +592,11 @@ static int do_pick_commit(struct commit *commit, struct replay_opts *opts)
         * write it at all.
         */
        if (opts->action == REPLAY_PICK && !opts->no_commit && (res == 0 || res == 1))
-               write_cherry_pick_head(commit, "CHERRY_PICK_HEAD");
+               update_ref(NULL, "CHERRY_PICK_HEAD", commit->object.sha1, NULL,
+                          REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
        if (opts->action == REPLAY_REVERT && ((opts->no_commit && res == 0) || res == 1))
-               write_cherry_pick_head(commit, "REVERT_HEAD");
+               update_ref(NULL, "REVERT_HEAD", commit->object.sha1, NULL,
+                          REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
 
        if (res) {
                error(opts->action == REPLAY_REVERT