diff hgext/record.py @ 16324:46b991a1f428

record: allow splitting of hunks by manually editing patches

It is possible that unrelated changes in a file are on sequential lines.  The
current record extension does not allow these to be committed independently.

An example use case for this is in software development for deeply embedded
real-time systems.  In these environments, it is not always possible to use a
debugger (due to time-constraints) and hence inline UART-based printing is
often used.  When fixing a bug in a module, it is often convenient to add a
large number of 'printf's (linked to the UART via a custom fputc) to the module
in order to work out what is going wrong.  printf is a very slow function (and
also variadic so somewhat frowned upon by the MISRA standard) and hence it is
highly undesirable to commit these lines to the repository.  If only a partial
fix is implemented, however, it is desirable to commit the fix without deleting
all of the printf lines.  This is also simplifies removal of the printf lines
as once the final fix is committed, 'hg revert' does the rest.  It is likely
that the printf lines will be very near the actual fix, so being able to split
the hunk is very useful in this case.

There were two alternatives I considered for the user interface.  One was to
manually edit the patch, the other to allow a hunk to be split into individual
lines for consideration.  The latter option would require a significant
refactor of the record module and is less flexible.  While the former is
potentially more complicated to use, this is a feature that is likely to only
be used in certain exceptional cases (such as the use case proposed above) and
hence I felt that the complexity would not be a considerable issue.

I've also written a follow-up patch that refactors the 'prompt' code to base
everything on the choices variable.  This tidies up and clarifies the code a
bit (removes constructs like 'if ret == 7' and removes the 'e' option from the
file scope options as it's not relevant there.  It's not really a necessity, so
I've excluded it from this submission for now, but I can send it separately if
there's a desire and it's on bitbucket (see below) in the meantime.

Possible future improvements include:

* Tidying up the 'prompt' code to base everything on the choices variable.
  This would allow entries to be removed from the prompt as currently 'e' is
  offered even for entire file patches, which is currently unsupported.
* Allowing the entire file (or even multi-file) patch to be edited manually:
  this would require quite a large refactor without much benefit, so I decided
  to exclude it from the initial submission.
* Allow the option to retry if a patch fails to apply (this is what Git does).
  This would require quite a bit of refactoring given the current 'hg record'
  implementation, so it's debatable whether it's worth it.

Output is similar to existing record user interface except that an additional
option ('e') exists to allow manual editing of the patch.  This opens the
user's configured editor with the patch.  A comment is added to the bottom of
the patch explaining what to do (based on Git's one).

A large proportion of the changeset is test-case changes to update the options
reported by record (Ynesfdaq? instead of Ynsfdaq?).  Functional changes are in
record.py and there are some new test cases in test-record.t.

--- a/hgext/record.py	Fri Mar 30 14:35:06 2012 -0500
+++ b/hgext/record.py	Fri Mar 30 22:08:46 2012 +0100
@@ -261,7 +261,7 @@
 def filterpatch(ui, headers):
     """Interactively filter patch chunks into applied-only chunks"""
 
-    def prompt(skipfile, skipall, query):
+    def prompt(skipfile, skipall, query, chunk):
         """prompt query, and process base inputs
 
         - y/n for the rest of file
@@ -271,14 +271,16 @@
 
         Return True/False and possibly updated skipfile and skipall.
         """
+        newpatches = None
         if skipall is not None:
-            return skipall, skipfile, skipall
+            return skipall, skipfile, skipall, newpatches
         if skipfile is not None:
-            return skipfile, skipfile, skipall
+            return skipfile, skipfile, skipall, newpatches
         while True:
-            resps = _('[Ynsfdaq?]')
+            resps = _('[Ynesfdaq?]')
             choices = (_('&Yes, record this change'),
                     _('&No, skip this change'),
+                    _('&Edit the change manually'),
                     _('&Skip remaining changes to this file'),
                     _('Record remaining changes to this &file'),
                     _('&Done, skip remaining changes and files'),
@@ -287,7 +289,7 @@
                     _('&?'))
             r = ui.promptchoice("%s %s" % (query, resps), choices)
             ui.write("\n")
-            if r == 7: # ?
+            if r == 8: # ?
                 doc = gettext(record.__doc__)
                 c = doc.find('::') + 2
                 for l in doc[c:].splitlines():
@@ -298,17 +300,69 @@
                 ret = True
             elif r == 1: # no
                 ret = False
-            elif r == 2: # Skip
+            elif r == 2: # Edit patch
+                if chunk is None:
+                    ui.write(_('cannot edit patch for whole file'))
+                    ui.write("\n")
+                    continue
+                if chunk.header.binary():
+                    ui.write(_('cannot edit patch for binary file'))
+                    ui.write("\n")
+                    continue
+                # Patch comment based on the Git one (based on comment at end of
+                # http://mercurial.selenic.com/wiki/RecordExtension)
+                phelp = '---' + _("""
+To remove '-' lines, make them ' ' lines (context).
+To remove '+' lines, delete them.
+Lines starting with # will be removed from the patch.
+
+If the patch applies cleanly, the edited hunk will immediately be
+added to the record list. If it does not apply cleanly, a rejects
+file will be generated: you can use that when you try again. If
+all lines of the hunk are removed, then the edit is aborted and
+the hunk is left unchanged.
+""")
+                (patchfd, patchfn) = tempfile.mkstemp(prefix="hg-editor-",
+                        suffix=".diff", text=True)
+                try:
+                    # Write the initial patch
+                    f = os.fdopen(patchfd, "w")
+                    chunk.header.write(f)
+                    chunk.write(f)
+                    f.write('\n'.join(['# ' + i for i in phelp.splitlines()]))
+                    f.close()
+                    # Start the editor and wait for it to complete
+                    editor = ui.geteditor()
+                    util.system("%s \"%s\"" % (editor, patchfn),
+                            environ={'HGUSER': ui.username()},
+                            onerr=util.Abort, errprefix=_("edit failed"),
+                            out=ui.fout)
+                    # Remove comment lines
+                    patchfp = open(patchfn)
+                    ncpatchfp = cStringIO.StringIO()
+                    for line in patchfp:
+                        if not line.startswith('#'):
+                            ncpatchfp.write(line)
+                    patchfp.close()
+                    ncpatchfp.seek(0)
+                    newpatches = parsepatch(ncpatchfp)
+                finally:
+                    os.unlink(patchfn)
+                    del ncpatchfp
+                # Signal that the chunk shouldn't be applied as-is, but
+                # provide the new patch to be used instead.
+                ret = False
+            elif r == 3: # Skip
                 ret = skipfile = False
-            elif r == 3: # file (Record remaining)
+            elif r == 4: # file (Record remaining)
                 ret = skipfile = True
-            elif r == 4: # done, skip remaining
+            elif r == 5: # done, skip remaining
                 ret = skipall = False
-            elif r == 5: # all
+            elif r == 6: # all
                 ret = skipall = True
-            elif r == 6: # quit
+            elif r == 7: # quit
                 raise util.Abort(_('user quit'))
-            return ret, skipfile, skipall
+            return ret, skipfile, skipall, newpatches
 
     seen = set()
     applied = {}        # 'filename' -> [] of chunks
@@ -326,7 +380,7 @@
             h.pretty(ui)
         msg = (_('examine changes to %s?') %
                _(' and ').join(map(repr, h.files())))
-        r, skipfile, skipall = prompt(skipfile, skipall, msg)
+        r, skipfile, skipall, np = prompt(skipfile, skipall, msg, None)
         if not r:
             continue
         applied[h.filename()] = [h]
@@ -342,12 +396,19 @@
                 idx = pos - len(h.hunks) + i
                 msg = _('record change %d/%d to %r?') % (idx, total,
                                                          chunk.filename())
-            r, skipfile, skipall = prompt(skipfile, skipall, msg)
+            r, skipfile, skipall, newpatches = prompt(skipfile,
+                    skipall, msg, chunk)
             if r:
                 if fixoffset:
                     chunk = copy.copy(chunk)
                     chunk.toline += fixoffset
                 applied[chunk.filename()].append(chunk)
+            elif newpatches is not None:
+                for newpatch in newpatches:
+                    for newhunk in newpatch.hunks:
+                        if fixoffset:
+                            newhunk.toline += fixoffset
+                        applied[newhunk.filename()].append(newhunk)
             else:
                 fixoffset += chunk.removed - chunk.added
     return sum([h for h in applied.itervalues()
@@ -372,6 +433,7 @@
 
       y - record this change
       n - skip this change
+      e - edit this change manually
 
       s - skip remaining changes to this file
       f - record remaining changes to this file