[PATCH v2] gitk: fix direction of symmetric difference in optimized mode

ee66e08 (gitk: Make updates go faster, 2008-05-09) implemented an optimized mode where gitk parses the arguments with rev-parse, and manually reads history in chunks. As mentioned in the commit message, symmetric differences are a problem there:

    One wrinkle is that we have to turn symmetric diff arguments (of the
    form a...b) back into symmetric diff form so that --left-right still
    works, as git rev parse turns a...b into a b ^merge_base(a,b).

However, git-rev-parse returns a...b in the swapped order

    b a ^merge_base(a,b)

This has been the case since at least 1f8115b (the state of master at the time of the abovementioned ee66e08; Merge branch 'maint', 2008-05-08). So gitk flipped the sides of symmetric differences whenever it was in optimized mode.

Fix this by swapping the sides of the reconstruction code.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
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This supersedes the older patch, which was simply wrong; the triangle directions in the affected section are correct.

The confusing part of this, but also how I stumbled across the real bug, was that I was playing with --show-all and that flipped the direction *again*. Turns out the option is not recognized by gitk and lets it go back to unoptimized mode, where the bug does not exist.

 gitk |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)