i18n: mark help strings for translation
The gettext function is just another name for the normal _ function
and it is used for translating docstrings when using _ would make
pygettext.py output a warning.
adding a
% default context
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -2,7 +2,7 @@
c
a
a
-b
+dd
a
a
c
% invalid --unified
abort: diff context lines count must be an integer, not 'foo'
% --unified=2
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -3,5 +3,5 @@
a
a
-b
+dd
a
a
% diff.unified=2
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -3,5 +3,5 @@
a
a
-b
+dd
a
a
% diff.unified=2 --unified=1
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -4,3 +4,3 @@
a
-b
+dd
a
% invalid diff.unified
abort: diff context lines count must be an integer, not 'foo'