bundle: introduce per-engine compression level

If experimental.bundlecomplevel.$engine is set, prefer it over the
generic experimental.bundlecomplevel. Given that compression levels have
widely different meanings across engines, this allows much saner
configuration.

Differential Revision: https://phab.mercurial-scm.org/D3393

mercurial/commands.py

@@ -1260,6 +1260,9 b' def bundle(ui, repo, fname, dest=None, *'
     # level without a) formalizing the bundlespec changes to declare it
     # b) introducing a command flag.
     compopts = {}
+    complevel = ui.configint('experimental',
+                             'bundlecomplevel.' + bundlespec.compression)
+    if complevel is None:
     complevel = ui.configint('experimental', 'bundlecomplevel')
     if complevel is not None:
         compopts['level'] = complevel

mercurial/configitems.py

@@ -440,6 +440,18 b" coreconfigitem('experimental', 'bundle2l"
 coreconfigitem('experimental', 'bundlecomplevel',
     default=None,
 )
+coreconfigitem('experimental', 'bundlecomplevel.bzip2',
+    default=None,
+)
+coreconfigitem('experimental', 'bundlecomplevel.gzip',
+    default=None,
+)
+coreconfigitem('experimental', 'bundlecomplevel.none',
+    default=None,
+)
+coreconfigitem('experimental', 'bundlecomplevel.zstd',
+    default=None,
+)
 coreconfigitem('experimental', 'changegroup3',
     default=False,
 )

tests/test-bundle-type.t

@@ -154,6 +154,11 b' Compression level can be adjusted for bu'
   $ f --size gzip-v2-level1.hg
   gzip-v2-level1.hg: size=475
 
+  $ hg --config experimental.bundlecomplevel.gzip=1 --config experimental.bundlelevel=9 bundle -a -t gzip-v2 gzip-v2-level1.hg
+  1 changesets found
+  $ f --size gzip-v2-level1.hg
+  gzip-v2-level1.hg: size=475
+
   $ cd ..
 
 #if zstd