| name | 0.4.6-understand-blob_object |
| description | [0.4.6] Type-1 git object storing raw file contents verbatim; identified by SHA-1 of content; no filename or metadata |
understand-blob_object
CALL NUMBER: git_internals_and_the_object_model.blob_object : deep_commit_object(8), deep_tree_object(8)
DEFINITION: Type-1 git object storing raw file contents verbatim; identified by SHA-1 of content; no filename or metadata retained.
Invoke this skill to understand blob_object down to its primitives. The RELATIVE ROOT below is the least-fixed-point closure of everything it bundles from — the full import cone, grouped by the lib each prim comes from. Projected from a prover-typed KB (MAP/SWI-Prolog consistency gate): every reference below resolves.
THE RELATIVE ROOT (the import cone, by lib)
from deep_commit_object
- commit_message_encoding_encoding_header (d2): Optional header line 'encoding ' in a commit object's raw text; git stores whatever the user wrote verbatim.
- commit_message_encoding_encoding_value (d3): The character encoding name stored in the encoding header (UTF-8, ISO-8859-1, Windows-1252, etc.); controls byte-to-character interpretation of the message bytes.
- commit_message_encoding_message_bytes (d4): Raw byte sequence forming the commit message body; decoded using encoding_value (or assumed UTF-8) to produce display characters.
- commit_message_encoding_original_encoding (d4): Alias for encoding_value; the encoding recorded at commit time distinguishing the message's original byte interpretation from the display encoding.
- commit_message_encoding_transcoding_logic (d4): git's internal conversion from the stored encoding_value to the requested log_encoding_flag encoding; uses iconv-style conversion with loss handling.
- commit_message_encoding_encoding_fallback (d5): Fallback behavior when transcoding_logic cannot map a character; typically replaces with a substitution character or skips the byte.
- commit_message_encoding_transcoded_message (d5): The output of transcoding_logic: message_bytes decoded then re-encoded into log_encoding_flag; git log emits this to the terminal.
- commit_message_encoding_display_encoding (d6): The terminal or output stream encoding git uses when writing the transcoded_message; git assumes UTF-8 output if terminal encoding is unset.
from deep_tree_object
- executable_file_mode (d3): Mode 100755; regular file with execute bits set; Git marks it this way to preserve the executable bit across platforms that handle it differently.
- mode_bit_format (d3): Base-8 positional numeral system used to encode file mode; Git stores exactly 6 octal digits representing 18 bits of mode information.
- mode_permission_bits (d3): The lower 9 bits (three octal digits) encoding Unix owner/group/other read-write-execute permissions; displayed as the last three digits of the 6-digit octal mode.
- mode_type_bits (d3): The upper bits of the octal mode identifying the entry's object category: regular file, directory, symlink, or submodule; encoded in the first two octal digits.
- regular_file_mode (d3): Mode 100644; standard blob-backed file with read permission for all and write for owner; the default for non-executable files committed to Git.
- subtree_mode (d3): Mode 040000; entry points to a nested tree object representing a directory; the tree entry name contains a forward slash but the slash is not stored in the entry itself.
- symlink_mode (d3): Mode 120000; entry points to a blob object containing the target path as raw bytes; the blob content is the symlink destination, not the link data itself.
- mode_zero_padding (d4): The leading zero in modes like 100644 and 040000 ensures consistent 6-digit width; the zero fills the third octal digit reserved for special file type flags.
from git_internals_and_the_object_model
- object_type_inspection (d1): git cat-file -t reveals object type; git cat-file -s shows byte size; git cat-file -p pretty-prints content; git rev-list walks commit graph.
- partial_clone (d1): Clone with --filter omitting blob objects from transfer; missing blobs retrieved on demand via fetch-object; enables huge-repository workflows.
- tree_object (d1): Type-2 git object listing directory entries as (mode, name, sha1) tuples; represents a single directory snapshot at a point in time.
- commit_filter (d2): Revision traversal predicate (--since, --author, --grep, --S, --G) restricting which commits appear in output.
- tree_entry_mode (d2): Octal mode in tree object: 100644 (regular file), 100755 (executable), 040000 (subtree), 120000 (symlink), 160000 (submodule).
- blob_prefetch (d2): Git fetch-object or protocol v2 advertisements retrieving missing blob content on demand from partial clone; requires server support.
- bundle_format (d2): Self-contained .git-bundle file encoding ref updates and reachable objects; enables offline transfer via removable media.
- promisor_ref (d2): Reference in a partial clone marking an object as promised but not yet fetched; enables placeholder usage before physical retrieval.
- submodule_pointer (d2): Entry in a parent repository's tree object referencing a specific commit of a nested repository; stored as mode 160000 with commit SHA-1.
- tree_entry_name (d2): Null-terminated byte string within tree entry; may contain slash for subdirectory entries; case-sensitive on all platforms.
- object_database (d3): Directory-backed key-value store under .git/objects/; loose objects stored as zlib-deflated files keyed by SHA-1; packed objects aggregated into packfiles.
- fsck_integrity (d4): git fsck traverses all reachable objects validating SHA-1 linkage, ref integrity, and accessibility; reports dangling and unreachable.
- loose_object (d4): Individual compressed file stored at .git/objects/xx/xxxx...; fast to write but inefficient at scale; one object per file.
- packfile (d4): Single binary file consolidating many objects via delta compression; named pack-*.pack with companion .idx index; vastly reduces repository size.
- delta_compression (d5): Git's storage optimization encoding an object as a series of copy/insert commands relative to a base object; OFS_DELTA uses relative offsets; REF_DELTA uses absolute SHA-1.
- packfile_bitmap (d5): Reachability bitmap at packfile end enabling fast network transfer negotiation and clone/fetch optimization by marking all reachable objects.
CONSUMERS (what needs this)
byte_string_content, clean_filter, index_file, sha1_hash, smudge_filter
Projected from the git internals and the object model KB (162 concepts / 159 relations) — consistency-typed by MAP; the facet list after the colon IS the cross-lib dependency web.
(leaf — this is an actual skill.)
