Source sweep: Use cmStrCat for string concatenation

This patch is generated by a python script that uses regular expressions to
search for string concatenation patterns of the kind

```
std::string str = <ARG0>;
str += <ARG1>;
str += <ARG2>;
...
```

and replaces them with a single `cmStrCat` call

```
std::string str = cmStrCat(<ARG0>, <ARG1>, <ARG2>, ...);
```

If any `<ARGX>` is itself a concatenated string of the kind

```
a + b + c + ...;
```

then `<ARGX>` is split into multiple arguments for the `cmStrCat` call.

If there's a sequence of literals in the `<ARGX>`, then all literals in the
sequence are concatenated and merged into a single literal argument for
the `cmStrCat` call.

Single character strings are converted to single char arguments for
the `cmStrCat` call.

`std::to_string(...)` wrappings are removed from `cmStrCat` arguments,
because it supports numeric types as well as string types.

`arg.substr(x)` arguments to `cmStrCat` are replaced with
`cm::string_view(arg).substr(x)`

1 files changed, 5 insertions, 6 deletions

diff --git a/Source/cmStringCommand.cxx b/Source/cmStringCommand.cxx
index 0f1adb3662..849a566b94 100644
--- a/Source/cmStringCommand.cxx
+++ b/Source/cmStringCommand.cxx
@@ -229,9 +229,8 @@ bool HandleAsciiCommand(std::vector<std::string> const& args,
     if (ch > 0 && ch < 256) {
       output += static_cast<char>(ch);
     } else {
-      std::string error = "Character with code ";
-      error += args[cc];
-      error += " does not exist.";
+      std::string error =
+        cmStrCat("Character with code ", args[cc], " does not exist.");
       status.SetError(error);
       return false;
     }
@@ -514,9 +513,9 @@ bool HandleCompareCommand(std::vector<std::string> const& args,
       (mode == "LESS_EQUAL") || (mode == "GREATER") ||
       (mode == "GREATER_EQUAL")) {
     if (args.size() < 5) {
-      std::string e = "sub-command COMPARE, mode ";
-      e += mode;
-      e += " needs at least 5 arguments total to command.";
+      std::string e =
+        cmStrCat("sub-command COMPARE, mode ", mode,
+                 " needs at least 5 arguments total to command.");
       status.SetError(e);
       return false;
     }