get_sha1: warn about full or short object names that look like refs

When we get 40 hex digits, we immediately assume it's an SHA-1. This
is the right thing to do because we have no way else to specify an
object. If there is a ref with the same object name, it will be
ignored. Warn the user about this case because the ref with full
object name is likely a mistake, for example

    git checkout -b $empty_var $(git rev-parse something)

advice.object_name_warning is not documented because frankly people
should not be aware about it until they encounter this situation.

While at there, warn about ambiguation with abbreviated SHA-1 too.

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

diff --git a/advice.c b/advice.c
index 780f58da0f5b508eaa278c98dd15bdf6f919c468..22abde9bc4edc5d90fa8e12e5e27654948955b23 100644 (file)
--- a/advice.c
+++ b/advice.c
@@ -12,6 +12,7 @@ int advice_commit_before_merge = 1;
 int advice_resolve_conflict = 1;
 int advice_implicit_identity = 1;
 int advice_detached_head = 1;
+int advice_object_name_warning = 1;
 
 static struct {
        const char *name;
@@ -29,6 +30,7 @@ static struct {
        { "resolveconflict", &advice_resolve_conflict },
        { "implicitidentity", &advice_implicit_identity },
        { "detachedhead", &advice_detached_head },
+       { "object_name_warning", &advice_object_name_warning },
 
        /* make this an alias for backward compatibility */
        { "pushnonfastforward", &advice_push_update_rejected }

diff --git a/advice.h b/advice.h
index fad36df467f065bf7ff7a82d9d447ee4ac5cecb9..24d5420b7add56e6b19ce58918bf8d2fbde8ed8d 100644 (file)
--- a/advice.h
+++ b/advice.h
@@ -15,6 +15,7 @@ extern int advice_commit_before_merge;
 extern int advice_resolve_conflict;
 extern int advice_implicit_identity;
 extern int advice_detached_head;
+extern int advice_object_name_warning;
 
 int git_default_advice_config(const char *var, const char *value);
 void advise(const char *advice, ...);

diff --git a/sha1_name.c b/sha1_name.c
index 95003c77ea9a0ee240d60bc7958bb48245b14ad4..502d107a5e427f61374a97d36ebc392f9619f3ad 100644 (file)
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -435,12 +435,31 @@ static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned l
 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 {
        static const char *warn_msg = "refname '%.*s' is ambiguous.";
+       static const char *object_name_msg = N_(
+       "Git normally never creates a ref that ends with 40 hex characters\n"
+       "because it will be ignored when you just specify 40-hex. These refs\n"
+       "may be created by mistake. For example,\n"
+       "\n"
+       "  git checkout -b $br $(git rev-parse ...)\n"
+       "\n"
+       "where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
+       "examine these refs and maybe delete them. Turn this message off by\n"
+       "running \"git config advice.object_name_warning false\"");
+       unsigned char tmp_sha1[20];
        char *real_ref = NULL;
        int refs_found = 0;
        int at, reflog_len;
 
-       if (len == 40 && !get_sha1_hex(str, sha1))
+       if (len == 40 && !get_sha1_hex(str, sha1)) {
+               refs_found = dwim_ref(str, len, tmp_sha1, &real_ref);
+               if (refs_found > 0 && warn_ambiguous_refs) {
+                       warning(warn_msg, len, str);
+                       if (advice_object_name_warning)
+                               fprintf(stderr, "%s\n", _(object_name_msg));
+               }
+               free(real_ref);
                return 0;
+       }
 
        /* basic@{time or number or -number} format to query ref-log */
        reflog_len = at = 0;
@@ -481,7 +500,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
        if (!refs_found)
                return -1;
 
-       if (warn_ambiguous_refs && refs_found > 1)
+       if (warn_ambiguous_refs &&
+           (refs_found > 1 ||
+            !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
                warning(warn_msg, len, str);
 
        if (reflog_len) {

diff --git a/t/t1512-rev-parse-disambiguation.sh b/t/t1512-rev-parse-disambiguation.sh
index 6b3d797ceabad069aefd1337ffe366b86b523412..db228086d3977d304a3debd7c3ae6dc54c40ad17 100755 (executable)
--- a/t/t1512-rev-parse-disambiguation.sh
+++ b/t/t1512-rev-parse-disambiguation.sh
@@ -261,4 +261,22 @@ test_expect_success 'rev-parse --disambiguate' '
        test "$(sed -e "s/^\(.........\).*/\1/" actual | sort -u)" = 000000000
 '
 
+test_expect_success 'ambiguous 40-hex ref' '
+       TREE=$(git mktree </dev/null) &&
+       REF=`git rev-parse HEAD` &&
+       VAL=$(git commit-tree $TREE </dev/null) &&
+       git update-ref refs/heads/$REF $VAL &&
+       test `git rev-parse $REF 2>err` = $REF &&
+       grep "refname.*${REF}.*ambiguous" err
+'
+
+test_expect_success 'ambiguous short sha1 ref' '
+       TREE=$(git mktree </dev/null) &&
+       REF=`git rev-parse --short HEAD` &&
+       VAL=$(git commit-tree $TREE </dev/null) &&
+       git update-ref refs/heads/$REF $VAL &&
+       test `git rev-parse $REF 2>err` = $VAL &&
+       grep "refname.*${REF}.*ambiguous" err
+'
+
 test_done