notebook/notes/git/objects.md

title	TARGET DECK	FILE TAGS	tags
Objects	Obsidian::STEM	fs::cas git	cas fs git

Overview

%%ANKI Basic What cryptographic hash function does git use internally? Back: SHA-1 Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic How many bytes make up a SHA-1 digest? Back: 20 Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic How many hexadecimal digits make up a SHA-1 digest? Back: 40 Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic How is a SHA-1 digest typically represented? Back: As a string of 40 hexadecimal digits. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What is "oid" an acronym for? Back: Object id. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What is an object id? Back: The digest produced when hashing/storing content. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What does it mean for git to be a content-addressed storage system? Back: Keys generated from hashing content are used to later retrieve said content. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014). Tags: fs::cas

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%%ANKI Cloze Interpreted as a key-value store, {oids} are to keys as {objects} are to values. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014). Tags: fs::cas

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%%ANKI Basic Why prefer term "oid" over e.g. "SHA-1 digest" or similar? Back: Git is transitioning to the use of other cryptographic hash functions. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What is a "porcelain" command? Back: A user-friendly command. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What is a "plumbing" command? Back: A lower-level command. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Cloze {Porcelain} commands are more user-friendly than {plumbing} commands. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What plumbing subcommand is used to generate an oid? Back: hash-object Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic The hash-object subcommand optionally stores the resulting object in what directory? Back: .git/objects Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Cloze The {object database} refers to the {.git/objects} directory. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What does the hash-object subcommand return? Back: The computed object id. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What optional functionality does the hash-object subcommand support? Back: It can write an object into the object database. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What flag lets the hash-object subcommand write to the object database? Back: -w Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic Where does object e.g. d670460b4b4aece5915caf5c68d12f560a9fe3e4 live in the object database? Back: At .git/objects/d6/70460b4b4aece5915caf5c68d12f560a9fe3e4. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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%%ANKI Basic What regular files exist in the object database after git init? Back: None. Reference: Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).

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References

• Scott Chacon, Pro Git, Second edition, The Expert’s Voice in Software Development (New York, NY: Apress, 2014).