comparison mercurial/helptext/internals/dirstate-v2.txt @ 48191:a5a673ec8f6f

dirstate-v2: Change the representation of negative directory mtime

Change it from how I previously thought C’s `timespec` works
to how it actually works.

The previous behavior was also buggy for timestamps strictly before the
epoch but less than one second away from it, because two’s complement
does not distinguish negative zero from positive zero.

Differential Revision: https://phab.mercurial-scm.org/D11629

48190:0cc0c0972164

  * Offset 31:
    12 bytes set to zero

  If an untracked node `HAS_MTIME` *set*,
  what follows is the modification time of a directory
  represented with separated second and sub-second components
  since the Unix epoch:

  * Offset 31:
    The number of seconds as a signed (two’s complement) 64-bit integer.

  * Offset 39:
    The number of nanoseconds as 32-bit integer.
    Always greater than or equal to zero, and strictly less than a billion.
    Increasing this component makes the modification time
    go forward or backward in time dependening
    on the sign of the integral seconds components.
    (Note: this is buggy because there is no negative zero integer,
    but will be changed soon.)

  The presence of a directory modification time means that at some point,
  this path in the working directory was observed:

  - To be a directory

48191:a5a673ec8f6f

  * Offset 31:
    12 bytes set to zero

  If an untracked node `HAS_MTIME` *set*,
  what follows is the modification time of a directory
  represented similarly to the C `timespec` struct:

  * Offset 31:
    The number of seconds elapsed since the Unix epoch,
    as a signed (two’s complement) 64-bit integer.

  * Offset 39:
    The number of nanoseconds elapsed since
    the instant specified by the previous field alone,
    as 32-bit integer.
    Always greater than or equal to zero, and strictly less than a billion.
    Increasing this component makes the modification time
    go forward in time regardless of the sign of the seconds component.

  The presence of a directory modification time means that at some point,
  this path in the working directory was observed:

  - To be a directory