util: add `nb_bytes` argument to `copyfile` to partially copy a file
When set, this allow to copy only the first `nb_bytes` of a file. This will be
useful for censor/strip operation with revlogv2.
Differential Revision: https://phab.mercurial-scm.org/D10798
--- a/mercurial/util.py Sun May 30 16:20:36 2021 +0200
+++ b/mercurial/util.py Sun May 30 18:08:52 2021 +0200
@@ -1909,7 +1909,9 @@
}
-def copyfile(src, dest, hardlink=False, copystat=False, checkambig=False):
+def copyfile(
+ src, dest, hardlink=False, copystat=False, checkambig=False, nb_bytes=None
+):
"""copy a file, preserving mode and optionally other stat info like
atime/mtime
@@ -1918,6 +1920,8 @@
repo.wlock).
copystat and checkambig should be exclusive.
+
+ nb_bytes: if set only copy the first `nb_bytes` of the source file.
"""
assert not (copystat and checkambig)
oldstat = None
@@ -1937,6 +1941,9 @@
if hardlink:
try:
oslink(src, dest)
+ if nb_bytes is not None:
+ m = "the `nb_bytes` argument is incompatible with `hardlink`"
+ raise error.ProgrammingError(m)
return
except (IOError, OSError):
pass # fall back to normal copy
@@ -1944,6 +1951,9 @@
os.symlink(os.readlink(src), dest)
# copytime is ignored for symlinks, but in general copytime isn't needed
# for them anyway
+ if nb_bytes is not None:
+ m = "cannot use `nb_bytes` on a symlink"
+ raise error.ProgrammingError(m)
else:
try:
shutil.copyfile(src, dest)
@@ -1960,6 +1970,10 @@
oldstat.stat[stat.ST_MTIME] + 1
) & 0x7FFFFFFF
os.utime(dest, (advanced, advanced))
+ # We could do something smarter using `copy_file_range` call or similar
+ if nb_bytes is not None:
+ with open(dest, mode='r+') as f:
+ f.truncate(nb_bytes)
except shutil.Error as inst:
raise error.Abort(stringutil.forcebytestr(inst))