filemerge: show actual capabilities of internal merge tools This information is useful to know which internal merge tools can be applied safely on binary files and/or symlinks.

filemerge: add config knob to check capabilities of internal merge tools For historical reason, Mercurial assumes capabilities of internal merge tools as below while examining rules to decide merge tool, regardless of actual capabilities of them. =============== ====== ======== specified via binary symlinks =============== ====== ======== --tool o o HGMERGE o o merge-patterns o (*) x (*) ui.merge x (*) x (*) =============== ====== ======== This causes: - unintentional internal merge tool is chosen for binary files via merge-patterns section of configuration file - explicit configuration of internal merge tool for symlinks is ignored unintentionally But on the other hand, simple "check capability strictly" might break backward compatibility (e.g. existing merge automations), because it changes the result of merge tool selection. Therefore, this patch adds config knob "merge.strict-capability-check" to control whether capabilities of internal merge tools should be checked strictly or not. If this configuration is true, capabilities of internal merge tools are checked strictly in (*) cases above.

filemerge: show warning if chosen tool has no binary files capability While matching patterns in "merge-patterns" configuration, Mercurial silently assumes that all merge tools have binary files capability. This implementation comes from 5af5f0f9d724 (or Mercurial 1.0). At failure of merging binary files with incorrect internal merge tool, there is no hint about this silent ignorance of binary files capability. This patch shows warning message, if chosen internal merge tool has no binary files capability. This will help users to investigate why a binary file isn't merged as expected.

filemerge: add the function to examine a capability of a internal tool For "symlink" and "binary" capabilities, _toolbool() can not examine these of internal merge tools strictly, because it examines only configurations in "merge-tools" section. Users can configure them explicitly as below for example, but this is not ordinary usage and not convenient: [merge-tools] :other.symlink = true :other.binary = true This patch adds hascapability() internal function, which can examine actual capabilities of a internal merge tool strictly. At this patch, hascapability() is still used with "strict=False". Subsequent patches use it with "strict=True".

filemerge: set actual capabilities of internal merge tools This information is used to detect actual capabilities of internal merge tools by subsequent patches. For convenience, this patch assumes that merge tools typed as "nomerge" have both binary files and symlinks capabilities.

help: describe more detail about capabilities while deciding merge tool "hg help merge-tools" describes as below: (internal merge tools) will by default not handle symlinks or binary files. But in some cases, Mercurial assumes that internal merge tools have one or both of these capabilities. "hg help merge-tools" also describes as below, for matching patterns in merge-patterns configuration section. But this is not sufficient. Here, binary capabilities of the merge tool are not considered. This patch describes more detail about capabilities while deciding merge tool.

tests: un-glob patchbomb test lines that were only globbing a hostname Differential Revision: https://phab.mercurial-scm.org/D4296

tests: force a stable hostname in patchbomb tests No visible output changes in this commit because everything is globbed away, but on Python 3 the stable hostname will mean that the headers don't trigger RFC2822 multi-line mode because they'll always be consistently short. Differential Revision: https://phab.mercurial-scm.org/D4295

patchbomb: allow using HGHOSTNAME to force a hostname I'll update run-tests.py to set this globally to stabilize some tests. The variable name is intentionally generic because I suspect we should generalize this to other tests. Differential Revision: https://phab.mercurial-scm.org/D4294

patchbomb: extract function for generating message-id Differential Revision: https://phab.mercurial-scm.org/D4293