Make sure we name temp files 'git-secret-*' (#428)

* pass mktemp a template on linux
* name tempfiles git_secret, not gitsecrets

src/_utils/_git_secret_tools_freebsd.sh

@@ -12,7 +12,7 @@ function __replace_in_file_freebsd {
 function __temp_file_freebsd {
   : "${TMPDIR:=/tmp}"
   local filename
-  filename=$(mktemp -t _gitsecrets_XXX )
+  filename=$(mktemp -t _git_secret_XXX )
   echo "$filename";
 }
 

src/_utils/_git_secret_tools_linux.sh

@@ -8,8 +8,9 @@ function __replace_in_file_linux {
 
 
 function __temp_file_linux {
+  : "${TMPDIR:=/tmp}"
   local filename
-  filename=$(mktemp)
+  filename=$(mktemp -t _git_secret_XXX )
   echo "$filename"
 }
 

src/_utils/_git_secret_tools_osx.sh

@@ -10,7 +10,7 @@ function __replace_in_file_osx {
 function __temp_file_osx {
   : "${TMPDIR:=/tmp}"
   local filename
-  filename=$(mktemp -t _gitsecrets_XXX )
+  filename=$(mktemp -t _git_secret_XXX )
   echo "$filename";
 }