Re: [PATCH v7 1/4] sha1_file.c: support reading from a loose object of unknown type

Update sha1_loose_object_info() to optionally allow it to read
from a loose object file of unknown/bogus type; as the function
usually returns the type of the object it read in the form of enum
for known types, add an optional "typename" field to receive the
name of the type in textual form and a flag to indicate the reading
of a loose object file of unknown/bogus type.

Add parse_sha1_header_extended() which acts as a wrapper around
parse_sha1_header() allowing more information to be obtained.

Add unpack_sha1_header_to_strbuf() to unpack sha1 headers of
unknown/corrupt objects which have a unknown sha1 header size to
a strbuf structure. This was written by Junio C Hamano but tested
by me.

Helped-by: Junio C Hamano [off-list ref]
Helped-by: Eric Sunshine [off-list ref]
Signed-off-by: Karthik Nayak <redacted>
---

diff --git a/sha1_file.c b/sha1_file.c
index 980ce6b..ac8fffc 100644
--- a/sha1_file.c
+++ b/sha1_file.c

@@ -1614,27 +1642,24 @@ static void *unpack_sha1_rest(git_zstream *stream, void *buffer, unsigned long s
  * too permissive for what we want to check. So do an anal
  * object header parse by hand.
  */
-int parse_sha1_header(const char *hdr, unsigned long *sizep)
+int parse_sha1_header_extended(const char *hdr, struct object_info *oi,
+                              unsigned int flags)
 {
-       char type[10];
-       int i;
+       struct strbuf typename = STRBUF_INIT;
        unsigned long size;
+       int type;

        /*
         * The type can be at most ten bytes (including the
         * terminating '\0' that we add), and is followed by
         * a space.
         */
-       i = 0;
        for (;;) {
                char c = *hdr++;
                if (c == ' ')
                        break;
-               type[i++] = c;
-               if (i >= sizeof(type))
-                       return -1;
+               strbuf_addch(&typename, c);
        }
-       type[i] = 0;

        /*
         * The length must follow immediately, and be in canonical

@@ -1652,12 +1677,39 @@ int parse_sha1_header(const char *hdr, unsigned long *sizep)
                        size = size * 10 + c;
                }
        }
-       *sizep = size;
+
+       type = type_from_string_gently(typename.buf, typename.len, 1);
+       if (oi->sizep)
+               *oi->sizep = size;
+       if (oi->typename)
+               strbuf_addbuf(oi->typename, &typename);
+       strbuf_release(&typename);

        /*
+        * Set type to 0 if its an unknown object and
+        * we're obtaining the type using '--literally'
+        * option.
+        */
+       if ((flags & LOOKUP_LITERALLY) && (type == -1))
+               type = 0;
+       else if (type == -1)
+               die("invalid object type");
+       if (oi->typep)
+               *oi->typep = type;