effectflag: store an empty effect flag for the moment
The idea behind effect flag is to store additional information in obs-markers
about what changed between a changeset and its successor(s). It's a low-level
information that comes without guarantees.
This information can be computed a posteriori, but only if we have all
changesets locally. This is not the case with distributed workflows where you
work with several people or on several computers (eg: laptop + build server).
Storing the effect-flag as a bitfield has several advantages:
- It's compact, we are using one byte per obs-marker at most for the effect-
flag.
- It's compoundable, the obsfate log approach needs to display evolve history
that could spans several obs-markers. Computing the effect-flag between a
changeset and its grand-grand-grand-successor is simple thanks to the
bitfield.
The effect-flag design has also some limitations:
- Evolving a changeset and reverting these changes just after would lead to
two obs-markers with the same effect-flag without information that the first
and third changesets are the same.
The effect-flag current design is a trade-off between compactness and
usefulness.
Storing this information helps commands to display a more complete and
understandable evolve history. For example, obslog (an Evolve command) use it
to improve its output:
x 62206adfd571 (34302) obscache: skip updating outdated obscache...
| rewritten(parent) by Matthieu Laneuville <matthieu.laneuville@octobus...
| rewritten(content) by Boris Feld <boris.feld@octobus.net>
The effect flag is stored in obs-markers metadata while we iterate on the
information we want to store. We plan to extend the existing obsmarkers
bit-field when the effect flag design will be stabilized.
It's different from the CommitCustody concept, effect-flag are not signed and
can be forged. It's also different from the operation metadata as the command
name (for example: amend) could alter a changeset in different ways (changing
the content with hg amend, changing the description with hg amend -e, changing
the user with hg amend -U). Also it's compatible with every custom command
that writes obs-markers without needing to be updated.
The effect-flag is placed behind an experimental flag set to off by default.
Hook the saving of effect flag in create markers, but store only an empty one
for the moment, I will refine the values in effect flag in following patches.
For more information, see:
https://www.mercurial-scm.org/wiki/ChangesetEvolutionDevel#Record_types_of_operation
Differential Revision: https://phab.mercurial-scm.org/D533
#!/bin/sh
# Script to get stable diff output on any platform.
#
# Output of this script is almost equivalent to GNU diff with "-Nru".
#
# Use this script as "hg pdiff" via extdiff extension with preparation
# below in test scripts:
#
# $ cat >> $HGRCPATH <<EOF
# > [extdiff]
# > pdiff = sh "$RUNTESTDIR/pdiff"
# > EOF
filediff(){
# USAGE: filediff file1 file2 [header]
# compare with /dev/null if file doesn't exist (as "-N" option)
file1="$1"
if test ! -f "$file1"; then
file1=/dev/null
fi
file2="$2"
if test ! -f "$file2"; then
file2=/dev/null
fi
if cmp -s "$file1" "$file2" 2> /dev/null; then
# Return immediately, because comparison isn't needed. This
# also avoids redundant message of diff like "No differences
# encountered" (on Solaris)
return
fi
if test -n "$3"; then
# show header only in recursive case
echo "$3"
fi
# replace "/dev/null" by corresponded filename (as "-N" option)
diff -u "$file1" "$file2" |
sed "s@^--- /dev/null\(.*\)\$@--- $1\1@" |
sed "s@^\+\+\+ /dev/null\(.*\)\$@+++ $2\1@"
# in this case, files differ from each other
return 1
}
if test -d "$1" -o -d "$2"; then
# ensure comparison in dictionary order
(
if test -d "$1"; then (cd "$1" && find . -type f); fi
if test -d "$2"; then (cd "$2" && find . -type f); fi
) |
sed 's@^\./@@g' | sort | uniq |
while read file; do
filediff "$1/$file" "$2/$file" "diff -Nru $1/$file $2/$file"
done
# TODO: there is no portable way for current while-read based
# implementation to return 1 at detecting changes.
#
# On bash and dash, assignment to variable inside while-block
# doesn't affect outside, because inside while-block is executed
# in sub-shell. BTW, it affects outside while-block on ksh (as sh
# on Solaris).
else
filediff "$1" "$2"
fi