revset: maintain ordering when subtracting from a baseset (issue4289)

cmdutil: separate building commit text from 'commitforceeditor' This separation makes it easier to extend/hook building commit text from the specified context. This patch uses 'committext' instead of 'edittext' for names of newly added variable and function, because the former is more purpose specific than the latter, even though 'edittext' in 'buildcommittext' is left as it is to reduce amount of diff.

convert: detect removal of ".gitmodules" at git source revisions correctly Before this patch, all operations applied on ".gitmodules" at git source revisions are treated as modification, even if they are actually removal of it. If removal of ".gitmodules" is treated as modification unexpectedly, "hg convert" is aborted by the exception raised in "retrievegitmodules()" for ".gitmodules" at the git source revision removing it, because that revision doesn't have any information of ".gitmodules". This patch detects removal of ".gitmodules" at git source revisions correctly. If ".gitmodules" is removed at the git source revision, this patch records "hex(nullid)" as the contents hash value for ".hgsub" and ".hgsubstate" at the destination revision. This patch makes "getfile()" raise IOError also for ".hgstatus" and ".hgsubstate" if the contents hash value is "hex(nullid)", and this tells removal of ".hgstatus" and ".hgsubstate" at the destination revision to "localrepository.commitctx()" correctly. For files other than ".hgstatus" and ".hgsubstate", checking the contents hash value in "getfile()" may be redundant, because "catfile()" for them also does so. But this patch chooses writing it only once at the beginning of "getfile()", to avoid writing same code twice both for ".hgsub" and ".hgsubstate" separately.

templates: escape NUL bytes in jsonescape (issue4303) It's currently possible for various fields to contain NUL bytes, which are disallowed in JSON.

localrepo: document localrepo.hook()

filemerge: use 'util.ellipsis' to trim custom conflict markers correctly Before this patch, filemerge slices byte sequence directly to trim conflict markers, but this may cause: - splitting at intermediate multi-byte sequence - incorrect calculation of column width (length of byte sequence is different from columns in display in many cases) This patch uses 'util.ellipsis' to trim custom conflict markers correctly, even if multi-byte characters are used in them.