merge with i18n

i18n-pt_BR: fix a few missing changes on 95304251c376

i18n-pt_BR: synchronized with 95304251c376

i18n-ja: synchronized with 1d7a36ff2615

patch: ensure valid git diffs if source/destination file is missing (issue4046) This is arguably a workaround, a better fix may be in the repo to ensure that it won't list a file 'modified' unless there is a file context for the previous version.

histedit: add description about exit code

rebase: add description about exit code when there are unresolved conflicts

shelve: remove unused variable assignment Fix test-check-pyflakes.t error after 1d7a36ff2615. This patch replaces "readshelvedfiles()" invocation by "shelvedfile().exists()" check and aborting, because it is required only to ensure that shelved changes corresponded to specified name exist after invocation. This patch also remove definition of "readshelvedfiles()" itself, because it is invoked only from the line removed by this patch.