This is the documentation file from Al Viro's "remapper" utility, taken
from the git repository in October, 2006.
diff-remap-data <dir1> <dir2> >map
git-remap-data <git-diff arguments> >map
will build information for remapper.
remap-log is a filter. It takes map as argument and, in the simplest form,
will look at the lines in stdin that have form
If the indicated line from old tree had survived into the new one, we will
on the output. If it hadn't, we get
Lines that do not have such form are passed unchanged. Default prefix
is "O:", but that can be changed by passing -o <prefix> in remap-log
That is already very useful for log comparison. E.g. if old-log is
from the old tree and new-log is from the new one, we can do
remap-log map <old-log >remapped-log
diff -u remapped-log new-log
and have the noise due to line number changes excluded.
Note that it's not just for build logs; the thing is useful for sparse logs,
grep -n output, etc., etc.
Ability to change prefix is useful when we are doing multiple remappings.
diff-remap-data old-tree newer-tree > map1
diff-remap-data newer-tree current-tree > map2
remap-log -o old: map1 <old-log | remap-log -o newer: map2>foo
* lines that didn't make it into the newer tree will be marked with old:
and otherwise left unchanged
* lines that made it to newer, but not the current will be marked with
newer: and have the filenames/line numbers remapped to newer tree
* lines that made it all the way will be remapped all the way
to current tree.
That's quite useful when you want to carry logs for a while, basically using
them as annotated TODO ("logs" here can very well be results of grep -n with
annotations added to them). You can have all still relevant bits stay with
the locations in text and see what had fallen out.
Note on relation to git: only git-remap-data needs it. Aside of working on
revisions in git repository instead of a couple of directory trees, it
generates slightly better map than diff-remap-data does. I.e. it manages
to remap more lines - it does notice renames.
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