tests/test-default-push.t

push: provide a hint when no paths in configured (issue3692)

When user type "hg push" command then this patch helps user by
providing hint if no default path is configured.

Second patch is the test coverage, to test the change behaviour of
first patch.

  $ hg init a

  $ echo a > a/a
  $ hg --cwd a ci -Ama
  adding a

  $ hg clone a c
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo b >> b/a
  $ hg --cwd b ci -mb

Push should provide a hint when both 'default' and 'default-push' not set:
  $ cd c
  $ hg push --config paths.default=
  pushing to default-push
  abort: default repository not configured!
  (see the "path" section in "hg help config")
  [255]

  $ cd ..

Push should push to 'default' when 'default-push' not set:

  $ hg --cwd b push
  pushing to $TESTTMP/a (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files

Push should push to 'default-push' when set:

  $ echo 'default-push = ../c' >> b/.hg/hgrc
  $ hg --cwd b push
  pushing to $TESTTMP/c (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files