Export of internal Abseil changes

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cf6037b985b629c253b8a87e4408c88a61baf89a by Abseil Team <absl-team@google.com>:

Adds an example of using ABSL_DEPRECATED on a template.
Without this, it's unclear where to add this annotation (e.g. before template <> or after it).

PiperOrigin-RevId: 270057224

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c53bc14dd683cc1e41c940a337001b42a0270eaf by Andy Getzendanner <durandal@google.com>:

Parser and unparser for command-line flags of type absl::LogSeverity.

PiperOrigin-RevId: 269939999

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d91174b02f3b213f0b26701d9d97c79f809e6fea by Abseil Team <absl-team@google.com>:

Fix a typo.

PiperOrigin-RevId: 269738777
GitOrigin-RevId: cf6037b985b629c253b8a87e4408c88a61baf89a
Change-Id: I6cec3101014e4c77f4ff2edb4c91740982dbb459

3 files changed, 51 insertions, 3 deletions

diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index fe59ec8..2bf562f 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -251,7 +251,7 @@ cc_library(
 )
 
 ############################################################################
-# Unit tests in alpahabetical order.
+# Unit tests in alphabetical order.
 
 cc_test(
     name = "commandlineflag_test",
diff --git a/absl/flags/marshalling.cc b/absl/flags/marshalling.cc
index f025ae7..f4ebe0e 100644
--- a/absl/flags/marshalling.cc
+++ b/absl/flags/marshalling.cc
@@ -16,6 +16,7 @@
 #include "absl/flags/marshalling.h"
 
 #include <limits>
+#include <type_traits>
 
 #include "absl/base/macros.h"
 #include "absl/strings/match.h"
@@ -186,4 +187,43 @@ std::string AbslUnparseFlag(const std::vector<std::string>& v) {
 }
 
 }  // namespace flags_internal
+
+bool AbslParseFlag(absl::string_view text, absl::LogSeverity* dst,
+                   std::string* err) {
+  text = absl::StripAsciiWhitespace(text);
+  if (text.empty()) {
+    *err = "no value provided";
+    return false;
+  }
+  if (text.front() == 'k' || text.front() == 'K') text.remove_prefix(1);
+  if (absl::EqualsIgnoreCase(text, "info")) {
+    *dst = absl::LogSeverity::kInfo;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "warning")) {
+    *dst = absl::LogSeverity::kWarning;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "error")) {
+    *dst = absl::LogSeverity::kError;
+    return true;
+  }
+  if (absl::EqualsIgnoreCase(text, "fatal")) {
+    *dst = absl::LogSeverity::kFatal;
+    return true;
+  }
+  std::underlying_type<absl::LogSeverity>::type numeric_value;
+  if (absl::ParseFlag(text, &numeric_value, err)) {
+    *dst = static_cast<absl::LogSeverity>(numeric_value);
+    return true;
+  }
+  *err = "only integers and absl::LogSeverity enumerators are accepted";
+  return false;
+}
+
+std::string AbslUnparseFlag(absl::LogSeverity v) {
+  if (v == absl::NormalizeLogSeverity(v)) return absl::LogSeverityName(v);
+  return absl::UnparseFlag(static_cast<int>(v));
+}
+
 }  // namespace absl
diff --git a/absl/flags/marshalling.h b/absl/flags/marshalling.h
index f9e2959..6d39180 100644
--- a/absl/flags/marshalling.h
+++ b/absl/flags/marshalling.h
@@ -33,6 +33,7 @@
 // * `double`
 // * `std::string`
 // * `std::vector<std::string>`
+// * `absl::LogSeverity` (provided here due to dependency ordering)
 //
 // Note that support for integral types is implemented using overloads for
 // variable-width fundamental types (`short`, `int`, `long`, etc.). However,
@@ -178,8 +179,8 @@ bool AbslParseFlag(absl::string_view, unsigned int*, std::string*);    // NOLINT
 bool AbslParseFlag(absl::string_view, long*, std::string*);            // NOLINT
 bool AbslParseFlag(absl::string_view, unsigned long*, std::string*);   // NOLINT
 bool AbslParseFlag(absl::string_view, long long*, std::string*);       // NOLINT
-bool AbslParseFlag(absl::string_view, unsigned long long*,
-                   std::string*);  // NOLINT
+bool AbslParseFlag(absl::string_view, unsigned long long*,             // NOLINT
+                   std::string*);
 bool AbslParseFlag(absl::string_view, float*, std::string*);
 bool AbslParseFlag(absl::string_view, double*, std::string*);
 bool AbslParseFlag(absl::string_view, std::string*, std::string*);
@@ -248,6 +249,13 @@ inline std::string UnparseFlag(const T& v) {
   return flags_internal::Unparse(v);
 }
 
+// Overloads for `absl::LogSeverity` can't (easily) appear alongside that type's
+// definition because it is layered below flags.  See proper documentation in
+// base/log_severity.h.
+enum class LogSeverity : int;
+bool AbslParseFlag(absl::string_view, absl::LogSeverity*, std::string*);
+std::string AbslUnparseFlag(absl::LogSeverity);
+
 }  // namespace absl
 
 #endif  // ABSL_FLAGS_MARSHALLING_H_