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    c1b7b2285522
    revlog: flag processor · c1b7b2285522
    Remi Chaintron authored
    Add the ability for revlog objects to process revision flags and apply
    registered transforms on read/write operations.
    
    This patch introduces:
    - the 'revlog._processflags()' method that looks at revision flags and applies
      flag processors registered on them. Due to the need to handle non-commutative
      operations, flag transforms are applied in stable order but the order in which
      the transforms are applied is reversed between read and write operations.
    - the 'addflagprocessor()' method allowing to register processors on flags.
      Flag processors are defined as a 3-tuple of (read, write, raw) functions to be
      applied depending on the operation being performed.
    - an update on 'revlog.addrevision()' behavior. The current flagprocessor design
      relies on extensions to wrap around 'addrevision()' to set flags on revision
      data, and on the flagprocessor to perform the actual transformation of its
      contents. In the lfs case, this means we need to process flags before we meet
      the 2GB size check, leading to performing some operations before it happens:
      - if flags are set on the revision data, we assume some extensions might be
        modifying the contents using the flag processor next, and we compute the
        node for the original revision data (still allowing extension to override
        the node by wrapping around 'addrevision()').
      - we then invoke the flag processor to apply registered transforms (in lfs's
        case, drastically reducing the size of large blobs).
      - finally, we proceed with the 2GB size check.
    
    Note: In the case a cachedelta is passed to 'addrevision()' and we detect the
    flag processor modified the revision data, we chose to trust the flag processor
    and drop the cachedelta.
    c1b7b2285522
    History
    revlog: flag processor
    Remi Chaintron authored
    Add the ability for revlog objects to process revision flags and apply
    registered transforms on read/write operations.
    
    This patch introduces:
    - the 'revlog._processflags()' method that looks at revision flags and applies
      flag processors registered on them. Due to the need to handle non-commutative
      operations, flag transforms are applied in stable order but the order in which
      the transforms are applied is reversed between read and write operations.
    - the 'addflagprocessor()' method allowing to register processors on flags.
      Flag processors are defined as a 3-tuple of (read, write, raw) functions to be
      applied depending on the operation being performed.
    - an update on 'revlog.addrevision()' behavior. The current flagprocessor design
      relies on extensions to wrap around 'addrevision()' to set flags on revision
      data, and on the flagprocessor to perform the actual transformation of its
      contents. In the lfs case, this means we need to process flags before we meet
      the 2GB size check, leading to performing some operations before it happens:
      - if flags are set on the revision data, we assume some extensions might be
        modifying the contents using the flag processor next, and we compute the
        node for the original revision data (still allowing extension to override
        the node by wrapping around 'addrevision()').
      - we then invoke the flag processor to apply registered transforms (in lfs's
        case, drastically reducing the size of large blobs).
      - finally, we proceed with the 2GB size check.
    
    Note: In the case a cachedelta is passed to 'addrevision()' and we detect the
    flag processor modified the revision data, we chose to trust the flag processor
    and drop the cachedelta.