Accept tags in HEAD or MERGE_HEAD

HEAD and MERGE_HEAD (among other branch tips) should never hold a
tag. That can only be caused by broken tools and is cumbersome to fix
by an end user with:

  $ git update-ref HEAD $(git rev-parse HEAD^{commit})

which may look like a magic to a new person.

Be easy, warn users (so broken tools can be fixed if they bother to
report) and move on.

Be robust, if the given SHA-1 cannot be resolved to a commit object,
die (therefore return value is always valid).

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/commit.c b/builtin/commit.c
index 1a653190b5f610fc5cd148c878e350973a0d0797..402eb5af53fbd8f4434e72d13f0be8330e667c47 100644 (file)
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1396,7 +1396,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
        if (get_sha1("HEAD", sha1))
                current_head = NULL;
        else {
-               current_head = lookup_commit(sha1);
+               current_head = lookup_commit_or_die(sha1, "HEAD");
                if (!current_head || parse_commit(current_head))
                        die(_("could not parse HEAD commit"));
        }
@@ -1431,6 +1431,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
                        pptr = &commit_list_insert(c->item, pptr)->next;
        } else if (whence == FROM_MERGE) {
                struct strbuf m = STRBUF_INIT;
+               struct commit *commit;
                FILE *fp;
 
                if (!reflog_msg)
@@ -1444,7 +1445,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
                        unsigned char sha1[20];
                        if (get_sha1_hex(m.buf, sha1) < 0)
                                die(_("Corrupt MERGE_HEAD file (%s)"), m.buf);
-                       pptr = &commit_list_insert(lookup_commit(sha1), pptr)->next;
+                       commit = lookup_commit_or_die(sha1, "MERGE_HEAD");
+                       pptr = &commit_list_insert(commit, pptr)->next;
                }
                fclose(fp);
                strbuf_release(&m);

diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index 75816329d6153c35e0763b35f70cfaf165f2a4b8..7e2f22589dcb14d5ba95ce1331ef816a458533d0 100644 (file)
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -293,7 +293,7 @@ static int do_fmt_merge_msg(int merge_title, struct strbuf *in,
                struct commit *head;
                struct rev_info rev;
 
-               head = lookup_commit(head_sha1);
+               head = lookup_commit_or_die(head_sha1, "HEAD");
                init_revisions(&rev, NULL);
                rev.commit_format = CMIT_FMT_ONELINE;
                rev.ignore_merges = 1;

diff --git a/builtin/merge.c b/builtin/merge.c
index f5eb3f549b3732c894016a83e3108df3b3f46d81..9567d60ba2d46e5f30cb6d954a74db8bcb5e9ee5 100644 (file)
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1036,11 +1036,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
                branch += 11;
        if (!branch || is_null_sha1(head_sha1))
                head_commit = NULL;
-       else {
-               head_commit = lookup_commit(head_sha1);
-               if (!head_commit)
-                       die(_("could not parse HEAD"));
-       }
+       else
+               head_commit = lookup_commit_or_die(head_sha1, "HEAD");
 
        git_config(git_merge_config, NULL);
 

diff --git a/commit.c b/commit.c
index ac337c7d7dc1724fa918f9340816d3102edb10bd..50fcf96c243c975a9c1be8443e84c7c4517cdc5b 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -39,6 +39,18 @@ struct commit *lookup_commit_reference(const unsigned char *sha1)
        return lookup_commit_reference_gently(sha1, 0);
 }
 
+struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name)
+{
+       struct commit *c = lookup_commit_reference(sha1);
+       if (!c)
+               die(_("could not parse %s"), ref_name);
+       if (hashcmp(sha1, c->object.sha1)) {
+               warning(_("%s %s is not a commit!"),
+                       ref_name, sha1_to_hex(sha1));
+       }
+       return c;
+}
+
 struct commit *lookup_commit(const unsigned char *sha1)
 {
        struct object *obj = lookup_object(sha1);

diff --git a/commit.h b/commit.h
index a2d571b97410fa857b4c177325c4556dac50fe3f..190c1d6883ad022cf90ae4f3dc21d5f939463181 100644 (file)
--- a/commit.h
+++ b/commit.h
@@ -38,6 +38,13 @@ struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
                                              int quiet);
 struct commit *lookup_commit_reference_by_name(const char *name);
 
+/*
+ * Look up object named by "sha1", dereference tag as necessary,
+ * get a commit and return it. If "sha1" does not dereference to
+ * a commit, use ref_name to report an error and die.
+ */
+struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name);
+
 int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size);
 int parse_commit(struct commit *item);
 

diff --git a/http-push.c b/http-push.c
index 28bfe768f7749e455f522fcfedeb2350da646416..d432b30379d3a91d9f5fb66d0768632688f86fac 100644 (file)
--- a/http-push.c
+++ b/http-push.c
@@ -1606,10 +1606,10 @@ static void fetch_symref(const char *path, char **symref, unsigned char *sha1)
        strbuf_release(&buffer);
 }
 
-static int verify_merge_base(unsigned char *head_sha1, unsigned char *branch_sha1)
+static int verify_merge_base(unsigned char *head_sha1, struct ref *remote)
 {
-       struct commit *head = lookup_commit(head_sha1);
-       struct commit *branch = lookup_commit(branch_sha1);
+       struct commit *head = lookup_commit_or_die(head_sha1, "HEAD");
+       struct commit *branch = lookup_commit_or_die(remote->old_sha1, remote->name);
        struct commit_list *merge_bases = get_merge_bases(head, branch, 1);
 
        return (merge_bases && !merge_bases->next && merge_bases->item == branch);
@@ -1680,7 +1680,7 @@ static int delete_remote_branch(const char *pattern, int force)
                        return error("Remote branch %s resolves to object %s\nwhich does not exist locally, perhaps you need to fetch?", remote_ref->name, sha1_to_hex(remote_ref->old_sha1));
 
                /* Remote branch must be an ancestor of remote HEAD */
-               if (!verify_merge_base(head_sha1, remote_ref->old_sha1)) {
+               if (!verify_merge_base(head_sha1, remote_ref)) {
                        return error("The branch '%s' is not an ancestor "
                                     "of your current HEAD.\n"
                                     "If you are sure you want to delete it,"

diff --git a/revision.c b/revision.c
index c46cfaa3e4d2f06fd67ccd71c7ba47891796fd60..5e057a0aedbc3106c0bd2199167f88bc56964e91 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -986,10 +986,12 @@ static void prepare_show_merge(struct rev_info *revs)
        const char **prune = NULL;
        int i, prune_num = 1; /* counting terminating NULL */
 
-       if (get_sha1("HEAD", sha1) || !(head = lookup_commit(sha1)))
+       if (get_sha1("HEAD", sha1))
                die("--merge without HEAD?");
-       if (get_sha1("MERGE_HEAD", sha1) || !(other = lookup_commit(sha1)))
+       head = lookup_commit_or_die(sha1, "HEAD");
+       if (get_sha1("MERGE_HEAD", sha1))
                die("--merge without MERGE_HEAD?");
+       other = lookup_commit_or_die(sha1, "MERGE_HEAD");
        add_pending_object(revs, &head->object, "HEAD");
        add_pending_object(revs, &other->object, "MERGE_HEAD");
        bases = get_merge_bases(head, other, 1);