Which git commands perform integrity checks?

Question

Trying to determine how quickly a user would be warned of corruption in the object database with git-1.7.4.1, I pulled a one-bit switcheroo:

$ git init repo
Initia         


        

Answer 1

In response to Mark Longair's answer, I fired up cscope and found:

(note how cscope has a curses interface and integrates nicely into Vim in case your interest was piqued)

Functions calling this function: parse_object

  File              Function                       Line
0 bundle.c          verify_bundle                   110 struct object *o = parse_object(e->sha1);
1 bundle.c          create_bundle                   242 struct object *object = parse_object(sha1);
2 bundle.c          create_bundle                   247 struct object *object = parse_object(sha1);
3 bundle.c          create_bundle                   323 obj = parse_object(sha1);
4 commit.c          lookup_commit_reference_gently   30 struct object *obj = deref_tag(parse_object(sha1), NULL, 0);
5 http-backend.c    show_text_ref                   372 struct object *o = parse_object(sha1);
6 http-push.c       one_remote_object               742 obj = parse_object(sha1);
7 http-push.c       add_remote_info_ref            1530 o = parse_object(ref->old_sha1);
8 log-tree.c        add_ref_decoration               93 struct object *obj = parse_object(sha1);
9 merge-recursive.c get_ref                        1664 object = deref_tag(parse_object(sha1), name, strlen(name));
a pack-refs.c       handle_one_ref                   43 struct object *o = parse_object(sha1);
b pretty.c          format_commit_one               835 parse_object(commit->object.sha1);
c reachable.c       add_one_reflog_ent              122 object = parse_object(osha1);
d reachable.c       add_one_reflog_ent              125 object = parse_object(nsha1);
e reachable.c       add_one_ref                     133 struct object *object = parse_object(sha1);
f reflog-walk.c     fake_reflog_parent              234 commit_info->commit = (struct commit *)parse_object(reflog->osha1);
g refs.c            peel_ref                        647 o = parse_object(base);
h refs.c            write_ref_sha1                 1452 o = parse_object(sha1);
i remote.c          ref_newer                      1482 o = deref_tag(parse_object(old_sha1), NULL, 0);
j remote.c          ref_newer                      1487 o = deref_tag(parse_object(new_sha1), NULL, 0);
k revision.c        add_head_to_pending             166 obj = parse_object(sha1);
l revision.c        get_reference                   176 object = parse_object(sha1);
m revision.c        handle_commit                   196 object = parse_object(tag->tagged->sha1);
n revision.c        handle_one_reflog_commit        855 struct object *o = parse_object(sha1);
o server-info.c     add_info_ref                     12 struct object *o = parse_object(sha1);
p sha1_name.c       peel_to_type                    508 o = parse_object(sha1);
q sha1_name.c       peel_to_type                    511 if (!o || (!o->parsed && !parse_object(o->sha1)))
r sha1_name.c       peel_onion                      573 o = parse_object(outer);
s sha1_name.c       peel_onion                      578 if (!o || (!o->parsed && !parse_object(o->sha1)))
t sha1_name.c       handle_one_ref                  698 struct object *object = parse_object(sha1);
u sha1_name.c       get_sha1_oneline                740 if (!parse_object(commit->object.sha1))
v tag.c             deref_tag                        16 o = parse_object(((struct tag *)o)->tagged->sha1);
w tree.c            parse_tree_indirect             271 struct object *obj = parse_object(sha1);
x tree.c            parse_tree_indirect             284 parse_object(obj->sha1);
y upload-pack.c     got_sha1                        342 o = parse_object(sha1);
z upload-pack.c     reachable                       382 parse_object(commit->object.sha1);
A upload-pack.c     receive_needs                   526 object = parse_object(sha1);
B upload-pack.c     send_ref                        644 struct object *o = parse_object(sha1);
C upload-pack.c     mark_our_ref                    670 struct object *o = parse_object(sha1);
D walker.c          loop                            182 parse_object(obj->sha1);

Answer 2

Here's how I would go about finding this out, although I'm not going to go through each source file to work out the conditions under which the check is performed. :)

Clone git's source code:

git clone git://git.kernel.org/pub/scm/git/git.git

Check out the version you care about:

cd git
git checkout v1.7.1

Look for that error message:

git grep 'sha1 mismatch'

That leads you to object.c and the parse_object function. Now look for that function:

git grep parse_object

... and go through the 38 files checking the conditions under which that function will be called.