view tests/svn/svndump-replace.sh @ 46667:93e9f448273c

rhg: Add support for automatic fallback to Python

`rhg` is a command-line application that can do a small subset of what
`hg` can. It is written entirely in Rust, which avoids the cost of starting
a Python interpreter and importing many Python modules.
In a script that runs many `hg` commands, this cost can add up.

However making users decide when to use `rhg` instead of `hg` is
not practical as we want the subset of supported functionality
to grow over time.

Instead we introduce "fallback" behavior where, when `rhg` encounters
something (a sub-command, a repository format, …) that is not implemented
in Rust-only, it does nothing but silently start a subprocess of
Python-based `hg` running the same command.
That way `rhg` becomes a drop-in replacement for `hg` that sometimes
goes faster. Whether Python is used should be an implementation detail
not apparent to users (other than through speed).

A new `fallback` value is added to the previously introduced
`rhg.on-unsupported` configuration key. When in this mode, the new
`rhg.fallback-executable` config is determine what command to use
to run a Python-based `hg`.

The previous `rhg.on-unsupported = abort-silent` configuration was designed
to let a wrapper script call `rhg` and then fall back to `hg` based on the
exit code. This is still available, but having fallback behavior built-in
in rhg might be easier for users instead of leaving that script "as an
exercise for the reader".

Using a subprocess like this is not idea, especially when `rhg` is to be
installed in `$PATH` as `hg`, since the other `hg.py` executable needs
to still be available… somewhere. Eventually this could be replaced
by using PyOxidizer to a have a single executable that embeds a Python
interpreter, but only starts it when needed.

Differential Revision: https://phab.mercurial-scm.org/D10093

#!/bin/sh

RSVN="`pwd`/rsvn.py"
export PATH=/bin:/usr/bin
mkdir temp
cd temp

svnadmin create repo
svn co file://`pwd`/repo wc

cd wc
mkdir trunk branches
cd trunk
echo a > a
mkdir d
echo b > d/b
ln -s d dlink
ln -s d dlink2
ln -s d dlink3
mkdir d2
echo a > d2/a
cd ..
svn add *
svn ci -m 'initial'
# Clobber symlink with file with similar content
cd trunk
ls -Alh
readlink dlink3 > dlink3tmp
rm dlink3
mv dlink3tmp dlink3
svn propdel svn:special dlink3
svn ci -m 'clobber symlink'
cd ..
svn up

# Clobber files and symlink with directories
cd ..
cat > clobber.rsvn <<EOF
rdelete trunk/a
rdelete trunk/dlink
rcopy trunk/d trunk/a
rcopy trunk/d trunk/dlink
EOF

python $RSVN --message=clobber1 --username=evil `pwd`/repo < clobber.rsvn

# Clobber non-symlink with symlink with same content (kudos openwrt)
cat > clobber.rsvn <<EOF
rdelete trunk/dlink3
rcopy trunk/dlink2 trunk/dlink3
EOF

python $RSVN --message=clobber2 --username=evil `pwd`/repo < clobber.rsvn

# Create d2 in branch so d2 has 'a' is in branch/d2 and trunk/d2,
# 'b' is in trunk/d2 and 'c' is in branch/d2
cd wc/trunk
echo b > d2/b
svn add d2/b
svn ci -m adddb
cd ..
svn up
svn cp trunk branches/branch
cd branches/branch
svn rm d2/b
echo c > d2/c
svn add d2/c
cd ../..
svn ci -m branch
svn up
cd ..

cat > clobber.rsvn <<EOF
rdelete trunk/d2
rcopy branches/branch/d2 trunk/d2
EOF
python $RSVN --message=clobberdir --username=evil `pwd`/repo < clobber.rsvn

svn log -v file://`pwd`/repo

svnadmin dump repo > ../replace.svndump