avoid to copy more than one file to the same destination file

mercurial/commands.py

@@ -790,6 +790,7 b' def docopy(ui, repo, pats, opts):'
     cwd = repo.getcwd()
     errors = 0
     copied = []
+    targets = {}
 
     def okaytocopy(abs, rel, exact):
         reasons = {'?': _('is not managed'),
@@ -803,7 +804,12 b' def docopy(ui, repo, pats, opts):'
     def copy(abssrc, relsrc, target, exact):
         abstarget = util.canonpath(repo.root, cwd, target)
         reltarget = util.pathto(cwd, abstarget)
-        if os.path.exists(reltarget):
+        prevsrc = targets.get(abstarget)
+        if prevsrc is not None:
+            ui.warn(_('%s: not overwriting - %s collides with %s\n') %
+                    (reltarget, abssrc, prevsrc))
+            return
+        elif os.path.exists(reltarget):
             if opts['force']:
                 os.unlink(reltarget)
             else:
@@ -829,6 +835,7 b' def docopy(ui, repo, pats, opts):'
                             (relsrc, inst.strerror))
                     errors += 1
                     return
+        targets[abstarget] = abssrc
         repo.copy(abssrc, abstarget)
         copied.append((abssrc, relsrc, exact))
 

tests/test-rename

@@ -76,3 +76,9 b' ln -s ba d1/ca'
 hg rename --force d1/ba d1/ca
 hg status
 hg update -C
+
+echo "# do not copy more than one source file to the same destination file"
+mkdir d3
+hg rename d1/* d2/* d3
+hg status
+hg update -C

tests/test-rename.out

@@ -101,3 +101,15 b' R d1/ba'
 # replace a symlink with a file
 A d1/ca
 R d1/ba
+# do not copy more than one source file to the same destination file
+copying d1/d11/a1 to d3/d11/a1
+d3/b: not overwriting - d2/b collides with d1/b
+removing d1/d11/a1
+A d3/a
+A d3/b
+A d3/ba
+A d3/d11/a1
+R d1/a
+R d1/b
+R d1/ba
+R d1/d11/a1